If the clasp does not provide sufficient adjustment (you should always try the clasp 1st since it is made to be adjusted), you have 2 options - take the bracelet to a Rolex watchmaker who has the tools, parts & experience to do the job correctly, or unbend the underside leaves of 2 links, remove/add links as necessary, & rebend the 2 original links back. Rolex used to have a special tool to perform this operation, but very few watchmakers still have them. In many cases, you can achieve more or less 'acceptable' results with a flat blade/screwdriver, but the work also tends to leave the exterior of the bended links warped/crumpled. I have attempted this twice & the links' external surfaces were left in a less than perfect state in both instances.