Recording from my yamaha mg10xu mixer and i want to have each track record seperately

I am new to this so please bear with me.
I am recording from my yamaha mg10xu mixer to the computer, I am using windows 10.
I want to put my mic on one track and music on another track.
2 questions
How do i lay down seperate tracks for mic and then music?
How do i then mix them after I tweak them?

Is it music that you are playing (such as a guitar), or do you mean that you have a pre-recorded “backing track”?

[u]Recording Multi-track Overdubs[/u].

Once you have multiple tracks open in Audacity they will automatically mix when you render (“export”).

If you want to monitor yourself with headphones while performing, it’s best to monitor directly through the mixer. There is always some latency (delay) through the computer and it can sometimes be tricky to get the latency down to an acceptable/unnoticeable level while still getting a good recording. So, it’s best (and easier) if you can avoid monitoring yourself through the computer. You should be able to get the backing-track into the mixer so you can hear it too. You’ll have to configure Audacity to play the backing-track into the mixer’s USB port, and you’ll also have to configure your mixer appropriately.

Your mixer sends the stereo mix to the USB port so you only get 2 channels. …You can can’t multitrack-record with that hardware, but you can record 1 or 2 tracks at a time and mix later.

Note that mixing is done by summation. (Analog mixers are built-around summing amplifiers.) So when you mix digitally in you generally need to lower the levels of each track to avoid clipping of the mix. Or, you can export to 32-bit floating-point which can go over 0dB without clipping, than re-import and use the Amplify (with a negative “amplification”) or Normalize to bring the levels down if necessary before exporting to your final format.

I am using a pre recorded track.
And I do import it but when I go to record the voice it starts to record at the end of the prerecorded track.

As it says here: Tutorial - Recording Multi-track Overdubs - Audacity Manual

In Audacity by default using the Record button will append record onto your existing track, see the Recording page.

In order to record on a new track, for multi-track overdubbing, you will need to use Shift and the Record button, or use its shortcut Shift + R.

You can change this in Recording Preferences by checking “on” the “Record on a new track”, doing this will make Audacity record on a new track with just the Record button and Shift and the Record button will append record onto your existing track.