Yes. If you have been using other calendar services, and you want to use them with Flo, you can connect to those calendar services and see them right alongside the Flo calendar. Just open Settings -> Accounts then tap on Add more accounts. Then select the account type you would like to connect to. After the account has been added, you will see calendar (or email) in corresponding view.
Flo doesn't actually import your events, it just connects to your existing calendar accounts so you can use them in Flo. You'll still be able to use and access your calendars just like you have been doing before from a calendar app or in your browser (e.g. Google Calendar.)