1- Log in to Canva and select your design.
2- Click on uploads.
3- Click the upload icon.
4- Select the digital paper you would like to use. I am using 903e6fb52e7975c8194b5b18e45f17e5 from 509554b57c228d2cd81019a294e36b1d
5- Your digital paper will appear in the uploads. Select it and the digital paper will appear on your design space. Resize to fit your area.
6- You can also add the digital papers to parts of layouts and grids.
7- Delete the image in the grid that you would like to add your digital paper, then with the grid selected click on your digital paper in the uploads section. The digital paper will now appear in your grid.