When you switch to Premium you can either create new Online Banking accounts or connect your existing ones to Online Banking. If you already have some history in your manual accounts, I'd advise you to connect them instead because Online Banking has a limit on how far it can reach into the past - it's either last 90 or 60 days of transactions.
If you'll connect your existing accounts to Online Banking, MoneyWiz will assume that everything that you have up until today is correct and that there are no "gaps" in there and will find the most recent transaction in your Account register and download from that transaction onwards. It means that if you have an account completely up to date, on first sync it will download nothing (but that's OK).
Note that it is possible that you've entered some manual transaction last Monday while your bank actually processed it on last Thursday - MoneyWiz might not catch this and download the duplicate. Therefore there might be a small cleanup work to do after the initial connection but if you've maintained good history of your accounts, it's quick and easy to do.
Also, don't worry - if something goes wrong, you can disconnect (not delete) you account from Online Banking and MoneyWiz will ask you if you want to keep or delete transactions downloaded from Online Banking. If you choose delete, your account will be brought back to the state as it was before you connected them.
As always, if you will require any assistance from us, please let us know!
You can read more here: https://wiz.money/knowledgebase/online-accounts/