You can take advantage of the scripts in /opt/webwork/webwork2/bin to help with this.
Make a copy of /opt/webwork/webwork2/bin/addadmin (e.g. addlocaladmin), and edit that file with the details for your new admin. Most of the field names in the script are self-explanatory. In the second line, the first argument of crypt is the plaintext password, so replace that instance of "admin" with the administrator's password (assuming that WeBWorK is managing passwords for you. If you're using an external authentication service you can delete that line).
Once you have your new addlocaladmin script you can run it as follows (replace [coursename] with the name of an individual course):
cd /opt/webwork/webwork2/bin
./wwsh [coursename] ./addlocaladmin
The following command should run the script on all of the courses on your server. I haven't actually tested this.
for coursename in `ls /opt/webwork/courses`; do /opt/webwork/webwork2/bin/wwsh $coursename /opt/webwork/webwork2/bin/addlocaladmin; done