You’ll need either a watch wrench or a pry tool. If you can post a model of the watch or some pictures of the back side we can help out better. Here’s a toolkit you can buy: https://www.amazon.com/Ohuhu-Professional-PCS-Watch-Repair/dp/B00PVN1DC0/ref=sxin_7?ascsubtag=amzn1.osa.6d3e2b31-a066-4527-83ae-574c59e2e882.ATVPDKIKX0DER.en_US&creativeASIN=B00PVN1DC0&crid=2HO2ZV3K3DA4T&cv_ct_cx=watch+wrench&cv_ct_id=amzn1.osa.6d3e2b31-a066-4527-83ae-574c59e2e882.ATVPDKIKX0DER.en_US&cv_ct_pg=search&cv_ct_wn=osp-single-source&dchild=1&keywords=watch+wrench&linkCode=oas&pd_rd_i=B00PVN1DC0&pd_rd_r=e4ee9427-5839-4411-9c96-49969279e639&pd_rd_w=HVTYU&pd_rd_wg=TiDiH&pf_rd_p=cfb8425e-590e-436e-8f8b-e7ed672784e6&pf_rd_r=79T0WX3JJH8CE4HYZ36Y&psc=1&qid=1592232090&sprefix=watch+wr%2Caps%2C185&sr=1-3-72d6bf18-a4db-4490-a794-9cd9552ac58d&tag=the-angle-20