If you order your first project online subscription, a project web app is automatically created in the background. The instance gets the following url: https://<yourtenant>.sharepoint.com/sites/pwa and inherits the language of your O365 tenant. This PWA is also linked to the project online tile, which everyone with a valid subscription can see. But, what if the PWA has the wrong language? Or the wrong URL? What if I want to enable the users an easy access vehicle to multiple PWAs (e.g. test, dev environment)? You‘ll get the answers in this blog post.by
There are two different adjusting screws to administer the project web app:
1) Within the respective instance you can change the site settings and pwa settings for a single site or site collection (if the prerequisites in Office 365 are done).
2) In the SharePoint Admin Center you can not only create and delete site collections, several PWA options in Project Online are also transferred to Office 365. Sounds a little bit like it was done in the Central Administration with an on-premise system, right? However, among other things in the SharePoint Admin Center you can change the permission mode, define quotas and control who’s able to see and edit the site collection settings in the PWA.