First, place a towel over an even table to avoid your glasses getting scratched. Second, open your glasses frame and place it on the table. Third, hold your glasses firmly with left hand, and use your right hand to insert a thumbtack between the frame and the lens where the nylon wire and frame meet right beneath the nose pad. Finally, wiggle the thumbtack untill the lens pop out.
You must go to the kits store to get a thumbtack first. Then just insert the thumbtack between the lens and frame to pop out the lens. If you can't do it by yourself, you can take your glasses to any optical store and the worker will help you remove the lens from your semi-rimless glasses.
Firstly, you should catch the end of the lens with a hook, and try to make the gap between lens and frame wider, in order that paper can be inserted, and then separate the lens from the frame with the silk paper. It requires the expertise of an eye care. I would like to inform you not attempt to remove eyeglass lens yourself because you may permanently damage the surface of your lens.
So easy for me, coz I own an eyewear shop. I can teach you a simple way, but I can not assure you to do it right. Coz you know, I have been doing this for years. First of all, you should realize the value of your glasses, if they are expensive, then I would rather you send them to an eyewear shop. However, if they are not, you can prepare your stuff now. Remember not to hold your lenses directly by your hands coz your nail may scratch your lenses. You can use a microfiber cloth to hold them. It is much safer and cleaner. If you are smart, I think the next step will be easier for you. You can use a screwdriver to loosen your glasses. This is the most difficult part as well as the key part. If you finish doing all of these, then congratulations to you, you have made it.