Go to Settings>Sync, tap the menu bars at the top right and add account.  Choose Toodledo and login using your Toodledo login credentials.  Allow it to perform a first time sync to populate in all your data from Toodledo.

When you create a new task in Informant, look at the top of the task entry to see where it's assigned to sync to.  Tap this to change it to your Toodledo account.