NicolettaA15 --
It sounds like you are a rookie Project Online application administrator, but good for you! And thank you for being brave enough to ask your question in this forum. You have come to the right place.
First of all, whomever created your organization's Project Online instance failed to make you an Administrator in the system. Right now Project Online thinks you are a team member, which is why you see so few items on the PWA Settings page. So, go back to your O365 app admin, or whomever created the Project Online instance, and ask him/her to make you an app admin for Project Online.
Once this is done, you will need to set the Permissions Mode setting to Project Permission Mode. To do this, navigate to the PWA Settings page and then click the Additional Server Settings link on the right side of the page. In the Permission Management section of the Additional Server Settings page, select the Project Permission Mode option, and then click the Save button. After you have done this, a new section named Security will appear at the bottom of the PWA Settings page.
In the Security section of the page, click the Manage Groups link and then click the Project Managers group to open it for editing. In this security group, add all of your PMs, and save the changes to the group. This will give your PMs access to Project Online.
Also, since you are a rookie Project Online administrator, I would strongly urge you to purchase the following book:
https://www.amazon.com/Ultimate-Application-Administrators-Project-Online/dp/099124642X/ref=sr_1_1?c...For total transparency, I was one of the co-authors of this book, but I do not receive any financial benefit from the sale of this book. This book is the ONLY user guide ever published for Project Online app admins, and contains around 900 pages of goodness and light about Project Online. I was the lead author for about 400 pages of content in this book, and one of the chapters I wrote is about how to control security in Project Online using Groups and Categories. I think you will find the book to be very useful. Hope this helps.