From the post screen you can usually see what info you need for the processor type and speed as well as how much RAM.
See this picture as an example, yours may not and probably doesn't look exactly like this, but it give you an idea. If your computer turns on to a picture instead you might be able to ge to the screen I think by pressing tab or something (it may tell you), or you can go into setup/BIOS settings (whatever it's called on your system) and press whichever button it says to push to get into the BIOS setup (most common buttons are delete or F2). On my laptop I have Phoenix BIOS and it displays all that info on the first page you come to. In some BIOS types you may have to go searching for it.