- You can have more than one (any) amount of remote repositories.
- Mercurial is DVCS (D - Distributed). Central/Main is just conventional repository, which all teammates use for intermediate code-storage (by agreement and workflow)
Synchronize toolbar (most right in toolbars, when enabled) is your best friend
- 1 in screenshot is for actions-button for data-transfer (read hints for buttons /and THG help/)
- 2 is section of defined remotes (in your case, after clone, you'll have only "default" alias), for which selected (by button) action will be performed
PS: from CLI it's a lot faster:
cd REPO_DIR
hg push