There are two ways we can make a site collection:
1. Through Central Administration
We show how to create site collection through Central Administration in Part 1 of this article. I’ll explain how to create site collection Programmatically (Using Visual Studio 2010) in this article.
1. Click on Start -> All Programs -> Microsoft SharePoint 2010 Products -> SharePoint 2010 Central Administration
2. Under Application Management, select Create site collections
3. Please add the details like Title, Description, URL and site template etc. (See into the screen shots for details)
4. Press OK Button.
5. After you press OK Button, You will see your newly created SharePoint 2010 Site Collection Successful Message.
6. Click on URL.
Thanks and Have fun!!