If you like to assign a flag on all the currently displayed referrals instead of doing so one by one, you can do so following the steps below.
1. Press on the Flag button under Mass Action section or press CTRL+SHIFT+G keys on your keyboard
2. Select which flag to assign
3. Press Update button
After this, all the currently displayed referrals will have the selected flag assigned.
IMPORTANT! This action will be applied on all the currently displayed referrals. To control which referrals to be displayed, you should consider applying filter first.