How to download multiple dimensions with world download feature?

So I've been working on a map recently, and I wanted to invite my friend over to help me. However, I'm not sure how we can download (with Aternos' world download feature) both the Nether and the Overworld, because I'm thinking of some parts of the map to be in the Nether. If anyone could tell me if this is automatically the case, or if it's possible and how to do it. That would be really helpful.

Also, we're gonna be using Forge for things like WorldEdit, if this might help.

Edit: It's been 2 hours, will anyone help?

Ok, thanks for informing me, I was just wondering because there were some comments on the video tutorial about downloading worlds saying they only got the Overworld file or something like that.