You can edit and delete the contacts' fields (i.e. parameters).
To manage the fields, go to "Subscribers" (1) and then click on "All subscribers" (2).
The all subscribers page opens, from there click in the center of the page on the button "Manage fields".
A page opens that shows all the fields currently in the database. From here, you can change the fields names and delete fields.
To change the name of a field, click on the field and write a new name. Then click on the save icon that appears at the end of the row.
To delete a field, click on the trash bin icon at the end of the row. When you delete a field, all the data for that field will be deleted from the database. Before deleting, be sure you are not using that field for sorting contact lists or for personalizing templates.