Collaborate on your family tree online

Click on the More tab.
In the Groups section of the More tab is a link called Manage groups. Click this link.
On the left should be a blue box for your group. A group was automatically created for you when you signed up. Click the "(Edit)" link next to the group's name.
You'll be taken to the Edit Group page. Since the group was created for you, you need to create your own password for the group.
On the edit group page, fill in the Password and Confirm Password fields and click the Submit button.
You'll be taken back to the Manage Groups page.
On the right side of the page is a Manage Groups section of links with a link named Invite others to your group. Click the link.
You'll be taken to the "invite others to join your group" page. Please be aware that anyone in your group will have the authority to make edits to your family tree.
Your name and email address will automatically be filled in. Click the "*Select Group" drop-down and select the group you want to invite people to. Most people only have one group, but you'll still need to selected it.
Fill in as many names and emails as you want, then read through the Invitation text. When you are ready, click the Send button.
The people you invited will then need to join your group using the information in the email they'll get sent.
Once someone has joined your group, any changes they make to the family tree will be automatically made to your family tree and vice-versa. You are both now editing the exact same tree.