Error In Phpmyadmin - error when selecting Auto Increment

As stated in Isac's error and comment, can only have a auto-increment field.

You can have other primary and / or foreign keys depending on your need.

For print, probably the id field of this usuarios table is auto-increment .

To confirm, click on above and you will have the flag of auto-increment :

If you want to change to the new column you are creating, uncheck it, and create another field with the flag marked.