Let see how to create a site collection and base site or Top level site for site collection.
Step 1 . Go To Sharepoint Central Admin
Step 2 . Go To Application Management Tab in Sharepoint Central Admin
Step 3 .Go to Site Management section and click on Create Site Collection
Step 4 .In Site creation page Select the Web application in which site is going to run.So it will use the same content DB of the specified web application.
Step 5 .Specify the title for the site.So that name will come as the site title.
Step 6 .Specify the URL for the site.If it is not base site then specify some meaning full name.
Step 6 .In this step you have to decide what kind of template i am going to use for mysite.There many template are available choose the appropriate one suites your business scenario.
Template Group Collaboration
This group contains template which suits your collboration need in your organization.Sites like Team collaboration,Wiki,Blog,Colloborative Document Workspace are available in this Group.
Template Group Meetting
This group Provides template for meeting includes basic meeting,social meeting,decision making meeting etc.
Template Group Enterprise
This group Provides template for catering some of the needs in enterprise functional need.Sites like Recod center,Report Center,Document Center etc
Template Group Publication
This group Provides template for creating publcation portal for your internet facing sites.
Step 7 .You have specify which user will be the administrator of the site.Specify the user which is going to do the administrative job for this site.
Step 7 .Specify the quota for the site.There by you can limit the growth of the site.
Step 8 .Submit the site creation form.After Successfull creation you will see following screen.
If you need to look at how to create web application Look at my BlogHow to Create Web Application