You realise your question encompasses what the entire music industry lives up to right?
If you want to learn how to record an instrument, you'll need to know how to use a mic, and what mic to use, and how to position it, and what preamps to send it through. Not to mention how to create melodies/harmonies, chord progressions, and in general write music.
If you want to know how to mix it together, you'll need to know how to layer tracks. If you're not using real instruments you'll need to learn who to use midi and software instruments, how to create beats, and find out which plugins provide the best software instruments. Plus after getting the sounds created you'll need to know how to use reverb and other effects, how to use compressors & limiters, how to EQ tracks and fit them in without conflicting with other tracks. Not to mention how to then master the tracks before exporting.
My suggestion, use royalty free music. There's a reason most people do it. I'm not saying it's a waste of time learning to produce music, but it gonna cost more time and effort that's necessary if you're just doing it to use it in your own videos. Not trying to be harsh, but if you really have "no experience" with music you're going to find yourself on a journey that'll take at least a few years to master.
If you really want to look at making your own music for your videos my advice would be to research all of the above mentioned things^ and learn how to produce music.
