Select the websites from the navigation bar, go to Site Designs, and to My Design Projects, and select any of the sites that you want.
Click anywhere on the screen to select the Section and Section Menu buttons to appear.
The Section Menu contains different other functions, now we need to Select the Template Block
Finally you can add the Template Block name, assign it a specific tag and save it.
Click on the section where you want to add saved blocks:
Then Click on Saved Section you will see the below window where you need to select Saved Blocks: