Hi Wentsi,
Adding a a field to a table adds it to the database, now you can add it to screens. To do this, go to Customize > Screens. Click on CRM_EditCustom to copy the screen. Note that the default screens cannot be edited (so that you can revert to them if needed), so you should make a copy of that screen. Go through the wizard, then on step 3 chose "Replace links to an existing screen". After this, find the name you in the wizard, and click it to edit the screen.specified
Now you can drag the Banner Store # field onto the screen. Due to the way this screen was designed, this new field will load and save once it is dragged onto the canvas, so you should be done with this screen. If you wanted to use this field on any other screen, you would have to add it there too.
For more information on editing screens, please see this webinar: https://www.youtube.com/watch?v=Q2eBgsAwPfg&list=PLG5Qmoh21vN4Od1mRtrDoY6NyPabWApjx&index=2, and any of the other webinars on: http://www.methodintegration.com/method/kb.aspx?folder=methodcrm&article=Method-V1&id=369.
-Russell