I was kind of skirting this in the other thread because while it isn't technically illegal it is the sort of thing that the cellphone companies just don't kin to. I do this sort of thing for fun to basically as many electronic devices as I can.

None of us here are going to be able to tell you how to do it. You'll want to google your phone model and "rooting" or "jailbreaking" and then spend like an afternoon reading documents until you come across at least 1 if not 2 complete sets of instructions. Read them all the way through before trying anything like this.

You are the one who should be doing this because you are the one who's going to get use out of it. These actions violate the warranty and may screw you out of your phone if you fuck up bad and brick it. If you don't, they might see that you've tweaked it, and will still void your warranty. Thankfully most phones can be restored to factory settings and there really isn't anything the people at the store can do or say about it.

What does rooting allow you to do? Install Free Programs, User Interface Tweaks, more powerful program management tools, as well as more efficient power meters and managers. What's possible is really based on what's available for your particular model and your particular phone OS flavor (unless you're developing the programs yourself). For some people this makes all the difference in the world; I like doing because I like seeing just how much versatility I can get out of these devices. For most though, if you have to ask how, it's generally recommended that you don't. RTFM (Read The Fucking Manual) and then, JFGI (Just Fucking Google It).