It is quick and simple to add a frame shape on iWi. 

Here is the process : 

Go to the product page of the desired frame and click on the Shapes tab
: Click on thebutton
: Name the shape, add its OMA file and click on the Add button
: Select the new shape in the dropdown list 
: Click on the Add button when you have selected it 
: Check that it appears in the shape table 
: Validate the addition of form by clicking on the Save button