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.