In order to edit an already created Recurring cost, go to the Management > Recurring costs panel and click on the blue link in the Cost type column representative of the desired row:
After that, a screen, similar to the one in the Recurring cost creation panel will show up. Moreover, you will be able to edit all the fields also in a similar way when you create a new recurring cost.
If you wish to create a new recurring cost, click here.
If you wish to delete a recurring cost, click here.