1972 Yamaha CS5 help

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Hi, I've recently come across what I believe to be a 1972 Yamaha CS5. My friends dad gave it to me. It's been sitting for the last 20 years idle.

It does "turn over".
I do not have the key so I'm not sure if it will start though I doubt it will.

I would like to bring this bike back to working condition. I'm wondering what my initial steps should be.. like what should I do first. I am not mechanically inclined and this will be my first project.

Should I clean the carbs? (I've heard that a lot).. or what.
I have the manual but it doesn't give any instructions on what I should do first.
Also how should I go about getting a key.

Thanks a lot and sorry for this post being so unorganized. Just a noob looking for some insight. All is appreciated.