I'm stuck at steps 3d. and 4. The instructions don't match the pictures and the walkthrough. I can't seem to complete this step. Any help would be appreciated.

I am unable to Set Up Contacts to Multiple Accounts, I'm currently going through the Accounts and Contacts module. When I get to steps:

"From Setup, enter Account Settings in the Quick Find box, then select Account Settings.
Select Allow users to relate a contact to multiple accounts."

I do not have the option to "allow users to relate contact to multiple accounts". I only have the following options:

Show View Hierarchy Link   
Enable Account Insights

Would appreciate some assisance :)