Hello Music_Freak, sorry I'm late, if the bottom of the panels have any rust on them, then can you clean them up and paint some anti rust on them, especially the thin bottom and ten pain with a paint that has anti-rust.
Probably a good time to clean out your shed, but I remember when I did this, I always wanted what I threw out the next day, so to speak.
I've given you this to look at 'assemble a tin shed where do I start' this might be easier than me trying to explain, but if someone can help you, that would be good.
Just quickly assemble one side with another and because the pop rivets may have been rusted, either use bigger rivots or screws to attach them together, any open holes can be filled with bog or place a rivet in them, not that they are doing anything and paint anti-rust paint over them.
If you moving the shed to a new position make sure you place plastic on the ground for the shed to sit on and before concrete is laid.
Try and brace these panels so if a wind suddenly comes it doesn't blow them over, and just be mindful of what you have painted, give them another coat, or perhaps have you used a small spray gun before, then paint the entire shed.
It's good practice for you to learn and it's not difficult, a hardware store sells them for $50 odd dollars or may be you know a friend who has one, but depends on your finance.
I would paint it first before the concrete is laid, but give it a few days to dry, by the natural atmosphere.
You can't dry it by a heating fan because if it's force fan dried (especially with oil based paint) it may crocodile on you, in other words the paint will look like crocodile skin and you'll have to scrape it all off, even though it may feel dry after a few hours, still give it a day or two to fully dry.
Let me know if you have any questions or I have missed out on something you want to know, I will look at this thread daily, like I should have been and very sorry.