if you purchased a usb 3.0 expansion card it should have came with some sort of instruction booklet. this would have the information you want.
that said: typical card installation most likely applies.
-turn the computer off & open case
-ground yourself to the case before touching components
-insert card into slot & attach to rear rail
-connect power cables (it uses 4 pin or other standard cables?)
-close case and turn computer on
-install provided drivers.
in some circumstances manufacturers want you to install drivers before physically installing the device. again, this is what the manual is for.