Metaball

You have two options to make a party: either party up after a played match with your random teammates and stick around or add Friends and search with them.

For the purpose of this guide, I'll cover the latter option.

Before you can create a party, you have to add some Friends. If they're on Xbox as well, then it's a matter of going to the Platform Friends section in the Friends tab, selecting "Add to Friends List" and waiting from them to accept it. In case whoever is playing with you is on a different platform, you'll have to manually insert the Meta Tag in the Friend Requests section in the Friends tab.

Once that's done, in the main menu press and invite whoever you're playing with to the party.

Note: Currently this achievement (and the one for 10 matches) pops when you load into the pre-game practice, meaning you might be able to do it much quicker than playing proper matches in a party.