Assuming this is the 1st floor- you figure out where exactly where you want the jack and then drill up from the basement into the cavity between the walls. You will be drilling through the subfloor and the bottom plate of the wall between 2 studs. On an interior wall one can study the subfloor from below to find the row of nails that are securing the bottom plate to the subfloor. If there is another outlet or heat duct nearby it makes an obvious point to measure from. (I like the cable outlet a few inches from the electric outlet).
If you are unsure of yourself, start with a very tiny (but long) drill bit to make sure you are coming up where you want to be. Small holes are easier to fix/hide if you miss your mark.