ok what you need to check is what your PSPs firmware is. either 1.0 or 1.5
- for the music, simply mount you PSP and go into the folder called "PSP" which holds your game data and stuff. now make a folder in there called "MUSIC" (of course without the quotes) and just drag and drop your MP3s into there. no special formats or anything, thats why they call it an MP3 player
- now for homebrew, just go to http://www.psp-hacks.com/downloads.php#homebrew and download some programs or emus you want. make a folder in "PSP" (right next to the "MUSIC" folder) called "GAME". now just drag and drop the game files you downloaded into the GAME folder. an example of your directories could look like PSP>GAME>DOOM>(all the doom game files and folders here)
- if you have FW1.5 you will need to make two folders for your games. for example DOOM and also DOOM% . a lot of homebrew will already have these folders already all set for you. if not you can get HomebrewPSP Converter that takes the EPBOOT file in the homebrews folder and makes a second one that you put in the appname% folder.
hope that helps