You can add or remove columns within your lists within the Design panel.
1. Click Design in the top gray navigation bar.
2. Select the page you would like to change the columns for. Click the List title from the right-hand sidebar. Then, use the Layout type field to change the view from rows to columns.
To change the number of columns that appear, adjust the scrolling option titled Columns.
4. Select Save and then Publish when you are ready to take your changes live!