Notepad 8FX Query

Malcspring

New member here,
Although I have been playing music for years. I have recently bought a Soundcraft Notepad 8FX as I am wanting to do a specific task with it and I am sure it is possible. The problem is I am strugggling with the routing of all the cables.
The bottom line is this. I have a Zoom Q2n video camera and I am wanting to video myself playing my bass guitar while playing along with some audio tracks stored on my computer. Get a good recording level of the bass in relation to the audio track that is on my computer using the Notepad 8FX then send the whole lot to the 3.5mm audio in on the Q2n.
In addition to this I am wanting to monitor the sound mix via the desk and hear the audio out of my Mackie CR4 computer speakers.
To me this is a very complicated thing and I really don't know if it is actually possible.
I have done a dummy run with my bass guitar where I have routed a cable from the bass head into one of the channels on the mixing desk and that has come through, however now I am wanting to play the audio from my computer and mix that to the bass guitar and send the whole lot to my Q2n and record it. It just won't allow me to play the audio through my Mackies. My routing is this. I have a 1/4 stereo jack running to a 3.5mm stereo jack running from the AUX on the desk, then this runs to either the 3.5mm headphone input on my computer or the AUX socket on my Mackies. I know that when you insert a plug into a headphone socket it normally cuts the sound. Maybe I need to see if there is a through option for the audio on my pc? Once I have done the recording to my satisfaction I was considering uploading them to my YouTube channel. Apologies if I appear a bit dumb. This is totally new to me. I know what I want to achieve. I just don't know if it is feasible with my equipment and also do I have the right skills and knowledge?
Thanks for any advice.