I tend to buy the outsize stuff, 50 or 70mm width. The surface you are going to tape needs to be pristine, so I clean it with isopropyl alcohol. Next, the type I use can be applied using soapy water. Make sure the area you are working in is as dust and draught free as possible. The tape is triple layered, with a backing film and a top film. Cut it to shape using sharp scissors and cut the corners rounded so it's less likely to lift at the edges. Soak the frame and the tape with the soapy water and remove the backing film, making absolutely sure you don't touch the adhesive surface. Press the tape on from the middle outwards, using a cloth and squeegying out any soap solution, and ensuring any bubbles are pushed outwards. Finally, using a hairdryer to make the tape more flexible press it on with a cloth from the upper surface them peel off the top protective layer.
If you use the dry type, again, make sure there's no dust and again press on from the middle outwards. This time use the hairdryer to warm the frame and the tape as you are applying it to keep it all flexible, especially on intricate shapes or curves. . As it cools it sort of shrinks onto the frame.
