Thanks for posting in the Community, we'd be happy to help and show you how to delete/edit a contact.
Once you're logged in please click on the "Contacts" option on the left hand side of the page. You can search for a specific contact, select a list to view the contacts in it, or scroll through your active contacts until you find the one in question. Once you have the contact displayed make sure to check the box next to the contact name (you can select multiple contacts at once.) That will allow you to select the "More Actions" tab and from there you can delete the contact(s).
To edit a contact just click on the contact's name or email address (for instance in the image above I would click on "Natalie B.") That will bring you to the contact's details page which looks like this:
Once you're on this page you can click right on the email address or contact name (depending on what you'd like to edit) which will allow you to change the information, and don't forget to click "Save" once the edits are complete.
I hope that helps!