There are two ways in which to set a fixed management fee for a tenancy. These will depend on if the tenancy is Let Agreed or Signed.
Firstly tenancy record, and then to Auto Charges (left hand side):
Within this screen you'll see two options in the upper right hand side:
If the Tenancy is Let Agreed, you'll need to use the +Add option, and in the subsequent pop up, set the trigger to be 'Upon Signing'.
However, if the tenancy is Live, you'll need to use the 'Add Date Specific Charge' and fill in like so(Fields are largely the same in both +Add and Add date specific.):
Once all applicable fields are complete, select Add Charge/ Add Date Specific Charge.
When set up correctly, the charge will then show in the Auto Charge section in Green. It should look similar to the below: