To add a new Product Attribute you will need to supply an Attribute Name and an Attribute Value.

Attribute Name:
This is the 'group' name of the attribute e.g. 'Size', 'Format', 'Type' etc

Attribute Value:
This is that actual value of one of the items in the group e.g. in the group 'Size' a possible value could be 'Small'.

To add the attribute click on the 'Add Attribute' button.  Once the attribute has been added successfully it will appear in the 'Current Attributes' list below the Add New Attribute area.

If you wanted to have a size attribute group with the values of 'Small', 'Medium' or 'Large', you would add three attributes with the name of 'Size' and the values of 'Small', 'Medium' and 'Large'.