You can invite other Hero's to your Friends list.
From the Social screen you can search Friends by their Name Code and add them to your Friends List. Name Codes can be found in the Settings screen, in the bottom left corner in capital letters.
You can also Favourite selected Friends so they appear at the top of your Friends list.
You can do this by clicking the Heart Icon next to their name.
Once a Player has been added as a Friend, you can then invite them to a Party to complete Co-Op Battles together.
For more information on Parties, click here