If this was me, I would log all the tapes with notes and do a rough outline (on paper) as to what I would like to have.
I would then go and do a rough cut (very rough tbh), putting all the content I want in a order that makes a bit of sense. you can then see how long it is, if its to long you know you can cut it down, if its to short then you might have to rethink your idea or find more footage to use.
I would choose some music (if you are going to have some) for background, montages etc then do another cut to the music getting closer to your final time limit-ish
Sit back give it a week or so go back watch it through and see if you like the way it is being told but have a open mind while doing this.
Do another refined edit of things you didnt like when you watched it back, move things around, change up the flow etc etc.
Watch again and keep doing the last step till your happy with output and story, making sure it wont bore someone watching or confuse them.
get a focus group (Friends, family) to watch it and let them be critical about it to see if they like, understand etc get there feedback and do a final cut.
Final stages are getting the sound levels and colours looking good then let people watch it
get a editor who knows how to tell a good story and ask them if they will help you edit the footage down or get their help in the last stages to refine it all.
There is a good course called Inside the Edit https://insidetheedit.com/ it is a little pricey but it will give you what you want I think, If I have the money I would do it but I just go with my feelings and the above