Have purchased the full version but can’t figure out how to create a challenge fleet and submit it. When I click on the Challenge button it lets me view challenges but no indication of how to build a scenario/fleet and submit it. Manual doesn’t explain it either. Help! 
It’s slightly counter-intuitive but pretty simple:
Go into a regular battle (or challenge for that matter), deploy your fleet as per, then hit the challenge button on the bottom of the screen.
Hope that helps.
Can you create a new battle scenario? Set the conditions, backdrop, etc?
you can through typing in a new scenario via modding. it can be a tedious process, though.