do not get sponges to paint - use rollers - they are useless unless you buy the really, really expensive ones. first, empty the room of everything you can and plonk the rest in the middle of the room in a pile and cover with old sheets (you can get these from charity shops if necessary - cheaper than diy stores).
hoover and dust the room throughout and the wash everything - doors, skirting, radiators, plugs etc to ensure everything is really clean. start on the ceiling and go around the edges carefully with a small brush - you do not need masking tape if you do it carefully and slowly with a steady hand (and don't slather the paint on - use a reasonable amount to cover well without streaks). then roller the main part of the ceiling and do two or three coats to cover well and let them dry for an hour or so in between (by the time you have done one or the other, they will probably be dry anyway).
finish ceiling off before you start on the walls. use the same format - do above the skirting and the corners, around plugs and up to the ceiling, and the roller in the middle bits. you will learn by trial about how much paint to use and how to best apply it as you are using brushes and a roller. have wet old cloths handy to wipe away any errors made in cornering and fine detail.
you will need white spirit to clean the brushes off and then lots and lots of rinsing down the sink to clean the rollers and brushes between each session of painting or changing colours. it may be best if you get two roller heads so they dry well in between washing, and a small and medium sized paint brush (x2 if desired) for edging.
basically, you learn by trial of fire and it is not rocket science- if you hit any issues then you can google or you tube for good hints and tips - i managed to change my bathroom light witch all by myself when t broke. i can't tell you how proud of myself i felt after doing it! go for it.....and use a couple of days off to do it a rest, but be prepared to be painting all day if it is a large room. good luck!!!