There are 2 option that you can create a new experience builder app
Option 1
use 9 dot ( quick launch navigation bar, in official ESRI term), then save as new app
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Option 2
use my content, create new app
Step 1
Step 2
Step 3
Step 4
Step 6