ijusth

I created an inventory tracking database. 21 fields, created the layouts and then decided I needed to add a number of additional fields. For example I had vendor contact but I wanted to add vendor contact phone number. I wanted to add PO#. I wanted to add besides the name of the person with the asset the department they worked for. I went into the layout mode and clicked on add field. It seemed that I could only add fields that were already in my table and can't seem to figure out how to add these additional items. What am I missing and how can I add these items? I know it is mind numbling simple but guess I am dense.

Thanks in advance.