First of all, I believe that you will need to have played through MyCareer to the point where you have joined an NBA team and have access to a calendar to select events.
I tried doing this with a spare account, but I couldn't invite my spare account to my squad. So I believe you will need to have a partner to unlock this achievement. You should have each other on your friend's list and be in the same park (read below).
From the main menu:
1. Select "MyCareer"
2. Press
to go to 2K Nav
3. Select "MyPARK"
4. You will be prompt to select which park to join. You can select whichever park, but make sure both players select the same park.
5. Press
6. Press
to see which of your friends are online
7. One person will need to scroll down and find your partner.
8. Press
and then select "Join park" or something like that.
9. You will then be in the same park as your friend. Repeat steps 5 to 7.
10. Press
and hopefully you will get an option to invite your friend to your squad
11. Your friend must press
and accept the invite
Once the partner accepts the invite, both players should unlock the achievement.
Note: If you and your friend are in different parks, one person should press
, select "MyPARK REP" and press
to abandon the park. You should then be able to select the same park as your partner.
WARNING: Abandoning the park will result in loss of all Rep and Rep Level Rewards.