To access the groups area, you need to go through "community", like this:
A group is essentially a mini-forum you can have all to yourself. Generally they will be to get together people who have something in common, for example
the musicians group is for people who like to make music.
To join a group, simply press this button:

which is located next to each public group. If you later decide that you no longer want to be part of the group, press this button:
To create a group, first click here:
That will either take you here:
If you're using your second account which is strictly for test purposes and so has no posts and therefore no group permissions, or here:
If you have the required 1000 posts.
You then name your group, describe it, and set how you want membership to be decided. If you want complete control over who's in and who's out then set it to "invite only". If you want anyone to be allowed in, select "public". If you want to approve people who ask to join, select "moderated".
You will then be asked to select a group icon. This is the image which will be associated with the group.
This is just like setting an avatar. You can either use a direct URL link or you can upload something from your computer. You must set an icon if you want your group to show up anywhere. If you don't then you can just press "skip".
You will then be taken to the main group page.
To use group functions
You will see on the main group page a few things. You will see this box:
Which tells you about the group. The group icon is displayed at the top, then the group creator, number of members, number of pictures uploaded to that group, and the number of discussions within that group. Clicking on the name of the "group maintained by" member will take you to that member's profile. Clicking on the number of members will give you a detailed list of all the members (you can also click "view all" by the members list below). Clicking on the number of pictures will take you to the group pictures. "group tools" at the top right also gives you all of these options.
You will also see:
Clicking "Post New Discussion" is just like posting a new thread, except only group members and moderators will be able to post there.
Clicking "add pictures" will allow you to add pictures to the group album. Note that you cannot post animations in this way. When you click the button, this window will appear:
Click "choose file" and select the file you want from your computer. Then click "upload". Close the window and the picture will become available.
If you are the owner of the group
then you will also have the admin options:
You can edit or delete the group here. You can also transfer the ownership to someone else. Note that only one person can own a group and have power over it. If you transfer power then you will not have any remaining power yourself. Mods will always have these powers but probably won't use them unless you use the report function in one of the discussions as usual. When transferring power this box will open:
Type in the name of the user you want to transfer to and press "send request". You cannot send the group to yourself, or to a member with less than 1000 posts. And as such I don't know what happens from here on in. No doubt someone will find out and tell me at some point.