If you have decided to fix a flex cable, you must have a good plan where to attach jumpers from and where they will lead to. Good jumper points are for example the sides of SMD components, or broader areas of the trace. I have circled a few potential points for jumpers for different traces in the picture, so that you get the general idea.
You must understand the concept of jumpers to successfully make a jumper on the flex. The wire has to be insulated, or you will end up with strange connections and damage. Enameled copper wire is something I personally use a lot, or sometimes pieces of scrap flex cable (more difficult).
See the next steps of the guide before cutting your jumper to get the general idea of what kind of a jumper you're looking to make.