Go to your Security folder, not under your database, but under the instance. Then expand Logins. Is your windows account listed there? If it is, right-click on it > Properties > Server Roles. Is 'sysadmin' and 'public' checked? If it is, you won't have to add your windows account to the database. The 'sysadmin' role gives your account administrative privileges over the entire instance (including all databases).
If your windows account is not listed under Logins, right-click on the Logins folder > New Login. Click the Search button and make sure 'From this location' is pointing to your network, and not the current server. You should then be able to add your login, and then grant it 'sysadmin' under Roles at the top left.