Braclet has come off watch.

There are tiny pins either side of the wrist band next to the clasp. Remove these pins and you can take out up to two links (and a half link on some models.)
A jeweller could do it, needs a special tool to tap them out and put them back

does this expand? or links.if its pins they need to be punched out, look inside there should be arrow.

use a fine pointed tip tool such as the prong of a fork and between links on bracelet there is a pin between each.. use prong to press out the pin

Raymond Weil watch braclet has a screw. Twist it, and then push from the other side. You may need to buy a set of basic tool for about 10 dollars from Amazon. Good luck and enjoy your watch. Alan Anderson

Sometimes the split ends of pins look like screws. If the slot is extremely thin its a pin A screw slot will be a bit wider. I pin removal toll inserted into the smaller end should do the trick.

You may or may not have arrows inside bracelet. Arrows are pointing the way the pins must come out.
First you have to find out what sort of pins or even screws are used to keep links together.
Examine both bracelet sides and find the side where pin ends have a groove.
Start with a tiny screwdriver and unscrew one of the screws. If it turns, but doesn't come out, that means you have a pins instead.
For removing pins the best would be pin removing tool (approx.5GBP on ebay), but it's possible to do the job without it.
Take a hardened steel needle and blunt the sharp end to the approx. size of pin end diameter using any sharpening stone or sandpaper. Get an old towel and fold it to make a soft base for work (like small cusion). As you don't have a special bracelet holder you will need a pair of helping hands to hold the bracelet steady upright. You will need small hammer and pair of flat nose pliers as well.
NOTE: The pins MUST be driven split end out first, not vice versa. Make sure that the grooved pin ends are facing towel, not the needle and hammer!!!
Now place the watch on the folded towel, take that needle and smallest hammer you have and start driving the pin out using light blows. Do Not hit hard, as you will brake the needle, scratch your watch or even injure yourself. Watchmakers are using 45 gram hammer, so, calculate your strength of blows.
After a few blows check if the split end is coming out and when you see that the end is long enough to grab it with pliers, pull the pin out with pliers. When pulling, do NOT turn pliers, as pins tend to brake when twisted. Use firm grip and your strength to pull the pin without twisting.
After shortening the bracelet or adding extra link(s) make sure that the pins go back EXACTLY the same way as they came out- the blunt end first in the hole and the split (grooved) end last. Before doing that check remaining pins in bracelet to make sure that you put them back from the right side of bracelet.
It is recommended to use plastic hammer to drive pins back in or you will scratch or damage bracelet. If plastic hammer is not available use an old toothbrush handle (or some plastic item) as an absorber. Simply put pin into the hole as deep as you can with your fingers, put the toothbrush handle on split pin end and hit handle, not the pin. 
Make sure that pin ends are flush with bracelet. If needed- hit few more times.
Job done!
If you do not want to do it yourself, any jeweler will do it in a matter of few minutes.
Don't forget to rate, please. 

Put the watch face down and examine the point where the band is connected to the watch case. you will find two holes and through them you will see sprinbar ends insertyed into watch case lugs. Take the tiny screwdriver and push the springbar end inwards,then do the same at the other lug reaching them through those holes.
Then repeat the same at the other end of the band.
Measure the distance between watch case lugs- this will be exact size for your new leather band.

Rate me, plesae.

Rolex is using screws instead of pins. Get the small screwdriver and unscrew the bracelet screws.
Do not forget to rate, please.

well your watch is most likely a watch that goes off by your body pumping so when you take it off it will stop soon after 

All Rolex watch bracelets has screws, not pins. Get small screwdriver and unscrew them.
If there is no screws at all, that means bracelet links had been removed and you have shortest version allready ,or, this is not the real (genuine) Rolex bracelet.
Find your nearest watchmaker to clarify all this.