The Builder Content Library can be accessed by the Word Tool and Excel Tool; however, their interfaces are different. 

1. In the Raw tab, go to Insert >> Doc Section >> From Builder Content Library 
2. Optionally enter the text you want to search for into the Search field 
3. Click on the Outline Tab and position your cursor in the row into which you want to add content 
4. In the Content Library window, double-click the content you want to add to the Outline