To add a supplier on an existing retailer open the retailer you would like to change.
Touch the "Supplier" icon here you will see all the suppliers this retailer has added currently to add a new supplier touch the "edit" icon.
Touch the "add" icon.
A scroll wheel will pop up select the desired supplier from the list and touch the "done" icon.
Now you will see the new supplier added in your suppliers list, however this change has not yet been saved.
To change an account number touch the bar containing the account number or TBA and a keyboard will pop up for you to input an account number touch "done" to complete this action. Once you are happy with your changes upload them by touching the cloud icon, this will save them.
Once your changes are uploaded you will see them in your supplier list.