If you have to ask for a guide, I suggest you have someone that has soldering experience do it for you. However, if you're dead set on doing it yourself then it's pretty simple. Just use a sucker or some desoldering braid to remove the old solder. Then add some new solder to each of the points. Make sure none of the points are touching. Also, while you have it open I would inpspect all the capacitors and make sure nothing has leaked onto the PCB and started to corrode things. Also, look for bulging caps as well.