If you want to share your family tree with someone, you need to click on the "Share" button on the bottom of your screen. Now you can choose whether the people you'll share the family tree will be able to edit the tree or just to view it (in your case you'll of course need to choose "Edit").
You can either share the family tree per E-Mail or just let the website generate a link you can copy and send to people.
For your family members to fully edit the family tree, they will need a familyecho.com account as well. Even if you selected "Edit" as a sharing option, users without an account will only be able to edit "themselves" (the person you had selected on the tree when you shared it).
However, a short note: You can't revoke editing rights (as far as I know) - so every person you shared your family tree with will infinitely be able to change the tree. Creating a back up of your family tree (via the "Save" option) periodically is never a bad idea, but it's especially important when other people are able to change the tree.
Hope this helps!
