Select
Windows Authentication from Authentication dropdownlist and click
Connect. Now you should be connected to the server.
During installation it must have asked you for authentication type for login such as
Windows Authentication, which is default and
SQL Server Authentication.
If you have missed this step, nothing to worry , go through the following link
Unable to login to SQL Server + SQL Server Authentication + Error: 18456[
^]
Hope that helps !
In case it doesn't resolve your problem, please let me know :)