Need help with Ubuntu VPS

I currently need some help with the new VPS I got for my irc bot  . The VPS runs on Ubuntu 11.10 x86(32 bit) and I need help with setting up java properly so the bot can work. I also need some help with learning how to use sessions or screens so the bot can stay on IRC even when I close down the terminal.

I've currently made the bot work and stay on IRC however I don't know how I did it exactly, and I also don't know how to take it off IRC  . I've also installed an excess amount of java packages which has occuppied alot of my VPS so I'm planning on cleaning it out and starting fresh again installing only what I need which is where I need help.

So would someone be able to help me setup java on my VPS and teach me how to keep the irc bot running even when I close Putty (terminal). I read it has something to do with screens and sessions to keep java programs running when the terminal is closed but I don't really know many commands or how to use it. So what commands should I be copying and pasting into the terminal? Or if it would be easier and I feel like I can trust you I could give you access to my VPS.