As you mentioned that you had already "created your database", I'm assuming that you will want to use that database rather than the Database.mdf file that is included in the DotNetNuke install App_Data folder. Other than for quick installs of DotNetNuke for testing purposes I do recommend that you create and use a database as you have done. And, since you created a login for database user "pattersonc", I'm assuming that you want DotNetNuke to connect to the database using Sql Server Authentication rather than Windows Authentication. Again, that is also my suggested approach.
However, since your are not able to connect to the database using SQL Server Authentication using that username and its associated password, there could be one of two problems:
1. Your install of SQL Server Express is not setup for SQL Server Authentication. To correct that . . .
a. Open SQL Server Management Studio Express and connect to the SQL server instance using Windows Authentication.
b. hover the mouse pointer over the top node (which gives the SQL server instance name) shown in the Object Explorer and right click
c. Select Properties from the context menu
d. Select the Security page from the list of property pages.
e. In the section titled "Server Authentication", select "SQL Server and Windows Authentication Mode" then click OK.
f. Close SQL Server Management Studio Express and restart MS SQL Server Express.
g. Open SQL Server Management Studio Express and try connecting to the database using SQL Server Authentication and the "pattersonc" username and password.'
2. The SQL Server login for user "pattersonc" has not been properly defined.
a. Open SQL Server Management Studio Express and connect to the SQL server instance using Windows Authentication.
b. Open the Security-->Logins Node under the top node then select the user "pattersonc".
c. Verify that the login name and password are correct AND that SQL Server Authentication is selected for that user. If not, make the necessary changes.
d. Select the database that you have created and open its Security-->Users node.
e. If you have not already added the "pattersonc" user, add it to the users for that database. Also check db_Owner in both the Owned Schemas and Database Role Membership boxes.
Again, try logging into the database in SQL Server Management Studio using SQL Server Authentication and the "pattersonc" user.
Once you are able to successfully complete the above, you should be able to successfully set up your database connecting and test it in the DotNetNuke install wizard. If you are still having problems, let us know what SQL Server information you are entering in the wizard and either correct them or advise how to manually modify the connectionStrings in web.config.