You can easily create a group for your Facebook Party from your smartphone or tablet via the Facebook App.
Go to the menu, scroll down to groups, then click create group.
Here, you can name the group, select the privacy settings and add a friend.
Next, the app will prompt you to: choose friends (you only need 1 to open the group), select a cover photo, add a description, and create your first post. After this, you will be taken to your group.
Continue in the Admin Tools section by clicking the Admin Badge icon in the upper right corner of the group.
Go to Group Settings then scroll down to Link Pages to make your business page an admin to this group.
You will still need to make PostMyParty a trusted app, and can only do this via the desktop version of Facebook. You can either switch to a computer to finish, or access the desktop version by trying these instructions.
As always, reflect who you are, keep it simple, and Have Fun!