Measure the jumper to easily reach the pad you're going for. Remember to route the jumper flat across the flex. If the flex needs to bend somewhere on the way, make sure the jumper wire is long enough. Also keep in mind that you should never use copper wire to repair flexes that need to move in the device, for it will without doubt, break.
Poke the wire a couple times with a file to expose copper if your earlier tinning is insufficient, and only enough to solder onto. And then tin the wire again.
Solder. Apologies for bad pic quality. In the second picture, I have also already cut the extra wire off.