Naomi --
The first thing you need to do is to create your Project Online login account in Microsoft Project. To do this, complete the following steps:
1. Click Microsoft Project and then open a new blank project, if needed.
2. Click File > Info > Manage Accounts.
3. Click the Add... button in the Project Web App Accounts dialog.
4. Enter a friendly name in the Account Name field, enter the URL of your Project Web App in the Project Server URL field, leave the "Set as default account" checkbox selected, and then click the OK button.
5. In the lower left corner of the Project Web App Accounts dialog, select the Choose An Account option, and then click the OK button.
6. Exit Microsoft Project completely and then relaunch the software.
7. In the Login dialog, click the OK button to connect Microsoft Project to Project Online.
From your description, it sounds like your enterprise Standard calendar is stuck in a Checked Out state. To force check it in, do the following:
1. Launch your preferred web browser and navigate to the Home page of PWA.
2. In the upper right corner of the page, click the Settings menu button (it looks like a gear wheel) and then select the PWA Settings item.
3. In the upper right corner of the PWA Settings page, click the "Force check in enterprise objects" link.
4. At the top of the page, click the pick list and select the Enterprise Calendars item.
5. Select the enterprise Standard calendar and then click the Check In button.
Once the enterprise Standard calendar is checked in, return to the PWA Settings page and click the Enterprise Calendars link at the top of the page. On the Enterprise Calendars page, select the Standard calendar and then click the Edit button. This action will launch Microsoft Project, connect it to Project Online, and then open the enterprise Standard calendar for editing. You will need to add all of your company's holidays as nonworking time for at least 5 years or so.
Also, the answer is "Yes" to the question about the "Allow master projects to be saved and published" option needing to be selected so that you can save your master project.
Naomi, if you need professional help with setting up and using Project Online in your organization, I would be grateful if you would allow me to compete for your business. I think I have already proven my skills and knowledge to you on this thread. Hope this helps.