How to Create a New SharePoint Online Site Collection
As a SharePoint Online Administrator, you have control over site collections. A site collection contains a single top-level site and multiple subsites below it that share common navigation, template galleries, content types, web parts, and permissions.
To create a new site collection, follow these steps:
Click the Manage link below SharePoint Online in the Microsoft Online Administration Center.
Click Manage site collections from the Administration Center window that displays.
You are taken to the Administration Center dashboard.
Click New from the action icons on the menu and then select Private Site Collection.
The New Site Collection window appears.
Enter the required information.
Click OK to go back to the SharePoint Online Administration Center dashboard.
When you create a new site collection, you are prompted to enter a value for the Resource Usage Quota. The value you enter in the box represents resource points that measure the effectiveness of custom applications running inside your site collection. For example, say you uploaded a custom web part that does a lot of calculations and uses up a lot of computing power.
SharePoint Online monitors how many resources your custom web part uses. The resource points that you assigned will authorize SharePoint Online to either leave it alone if it’s performing within the quota, throttle it if the code is poorly written and starts to hog all the resources, and ultimately kill the web part or make the application stop running if it goes haywire and starts to cause problems.
Fortunately, the killing only happens within the affected site collection and has no impact in other site collections within the tenancy.