Just insert the fishing line into the small holes near the bridge of the glasses, on the inside, and hold the line still and taught near the bridge of the nose. Take the other end of the line, from the inside, and wrap in the other hole on the other side; Insert the lens into the built-in groove in the frame and tighten the line against the lens, in the groove in the lens and cut off the excess fishing line.
Most rimless glasses have lenses fixed with a single wire, you should insert one end of the wire into glasses hole near the pad arm and insert the other end to the opposite side of the glasses, then tie the knot.
There are many tools and materials you need to repair the rimless glasses, such as fishing wire, tweezers, utility scissors and so on. So I suggest you to repair them in the local optical store or get a new pair.