Transfer from/to Another Account
Simply choose the other bank account from the dropdown, just as you would in FreeAgent.
FreeAgent will do exactly what it does when you explain a bank transfer in FreeAgent (documented by FreeAgent here).
We always recommend doing a dry run (by clicking the Dry Run button) to see whether your rule does what you want.
Transfers between accounts with different currencies
FreeAgent will convert the amount automatically (using rates from xe.com). You can always adjust the converted amount later on if you need to – this is also described in FreeAgent's docs linked above.