Bring up the memo detail view for the memo you wish to return from. http://help.dcit.com/en/articles/2017041-how-do-i-view-the-memos-i-have-created-for-my-clients

Click the gear icon and choose the Restock from  this Memo option.

You will be teleported to the Restock from this memo screen.  

From here you can utilize the various tools to choose the items you wish to restock.

If you want to restock (return) all items simply click the Restock All button and this will adjust the restock qty for all items.

Alternatively you can utilize the restock arrows to adjust the restocked qty of any items you need to restock (return).

You can also adjust the restock qty field manually if you need.

Once you have set your restock qty's simply click the save icon to complete the process which will return those items back into inventory.