Plug your Direct in box's USB cable into your computer's USB port.
Install any software that came with the Direct in box, if necessary.
Plug your guitar cable into your guitar and into the Direct in box's input. Make sure your input and output volumes on the Direct in box are both up relatively high (have the knob pointing to at least 12:00).
Open your recording software program. Make sure the input that the program is using is your direct in box. Begin recording a track and strum your guitar. Play the track back to make sure your levels are not too high or low. If they're too high, you will get a loud, fuzzy sound when you play. If they're too low, you might not hear anything. Adjust the output volume on the direct in box to higher or lower, depending on what you need.
Cut, paste, compress and EQ the track just like you would a MIDI instrument when you're finished recording. There should be no background noise on the track at all, and you should also be able to add effects, providing your software allows you to.