If your grandmother is deceased and you manage her profile you can add her test information from her profile. Just click on her Wiki-ID at the top right of her profile, then click on DNA. Click on the DNA Test tab and follow the directions.
If your grandmother is living, (and she appears to be) for privacy reasons she must enter her own DNA test information. You can invite her to join Wikitree by adding her email to her profile. Once she has joined and added her test information she can turn her profile over to you to manage.