Anyone can create a profile for any scientist. Once a profile (called a 'node') is created, any user can add interpersonal connections (such as collaborators, mentors, and trainees) to that node. However, once a node is created, you can only edit the biographical data, website information, and Google search terms if you link that node to your account, effectively telling Academic Tree that you are that node. This becomes important if someone else creates nodes for scientists other than themselves.
Therefore, it is best to create your own profile and provide the information you see fit, before someone else creates a node for you, potentially populating your profile with incorrect or incomplete information, or even leaving it blank. That way, you can be sure that the correct biographical information is included, and to a level that you prefer.
When you first register a new account with AcademicTree, you have the option of associating your account with an existing node. However, if you are creating your own node, at the bottom of the page after you first log in, you have the option to add your biographical details, as seen here:
The AcademicTree tutorial shows a very different webpage in their own tutorial. That is shown below.