Attach Database is disabled in Microsoft SQL Server 2012 Management Studio
If you need help attaching via T-SQL, if you see the SCRIPT button on the image you attached, you will be able to output the SCRIPT syntax to attach via 'T-SQL'. Just fill it in with the required information like target path to MDF file etc.. Give that a shot and see what you can come up with.

Also make sure you are on the same version of SSMS as the database to help prevent issues.

Also, when you connect to the DB instance, make sure you are using a Administrative account, it might be different than your current log-in or Windows Auth account.