Hi Francis...
I don't have this interface but a quick look at the manual on-line suggests some advice.
You would normally need to use the mic/instrument input with the switch set to guitar/bass not the line level input, which is for synths, drum machines etc.
Ensure that the phantom power switch is off.
Increase the input level (the output level is for sends to headphones/speakers for monitoring purposes.
Connect the interface to your computer via a usb cable - Studio One will only see an input from the interface and probably won't distinguish between line or mic/guitar inputs.
You cannot increase the record level input volume into S1 from the S1 software this must be done at source (the instrument/interface).
Make sure you have the track record channel set to receive from the interface, arm for recording and engage the blue monitor button for the track so that you can hear what's being recorded (presumably monitoringvthrough headphones to reduce feedback).

This is a discontinued interface originally designed for Windows Vista, not sure if it is still class compliant for later OS'...?!!

For future reference, it always helps to include your equipment/software specifications.

Regards.....