That's a pretty broad question and it's been explained before, so I'd suggest looking through the tutorial section, consulting readme files where necessary and running a search here in the NBA Live 08 section for specific patches. However, in a nutshell:
- Most art updates are placed in the sgsm folder (C:\Program Files\EA Sports\NBA Live 08\sgsm). However, if you have a .viv file, they are placed in subfolders within sgsm (jerseys go in the uniforms folder, courts go in the stadia folder). Usually if anything more complicated is required, the patch will have a readme file with installation instructions.
- Roster patches are placed in the saves folder, which is located within the NBA Live 08 folder under your Documents.
On a side note, I've noticed you creating a couple of threads with "help needed" and the like in the title. While this isn't against the rules, it's not recommended as it's a very generic subject and if you use it over and over again, it can get confusing for anyone looking to respond when there's multiple threads that just ask for help in their title. I'd recommend that you put a little more detail into the subject ("Need help installing patches", for example); it makes things easier for everyone and should yield better responses.