Migrate All Data
Informant Sync on iOS has an automatic migration assistant that makes it simple to move from Apple Calendar, Apple Reminders, Google Calendar, Google Task, Toodledo or unsynced data to Informant Sync. 
  1. Make sure you are logged into your Informant Sync Account at informant settings>accounts>informant sync
  2. Tap the sync option to force it to complete a sync and make sure your last sync date updates to today and you have a current expiration date shown.
  3. Select Migrate Data at the bottom of that same page
  4. Select which existing sync account you wish to migrate the data over to Informant Sync.
Once this procedure is finished your data will be moved from wherever it was synced to previously into informant sync.

Please note that once the data is migrated there is no way to reverse the process. 

MIgrate individual events or tasks
Alternatively, if you only want to move specific events or tasks to informant sync you would edit the event in informant and at the 'calendar' option choose a calendar under the informant sync header. For a task, tap the project option in your edited task and choose a project under the informant sync header.

Migrate an specific calendar
This will only work with google calendars or currently unsynced calendars. To move calendars from google to Informant Sync, then you would first have to "unassign" the Calendar from its current sync account

Sync Settings >calendars triggers more>manage calendars>select the calendar under the google calendar header>sync to>choose none.

Then you can assign that calendar (or any other unsynced calendar) to the Informant Sync account. Go back to sync settings >calendars triggers more>manage calendars>select the calendar under the unsynced calendar header>sync to>choose informant sync.