Sql Express 2012 Upgrade to SP1

I have Sql Server Express 2012 installed on one server. As I'm trying to install TFS 2015 and it require Sql Express 2012 with SP1 I would like just to update my instance to SP1, but I can't find a way.

From MS website I see this (at this link):

Installation for the Existing Users

If you have an existing installation of Express with Tools, SQL Server Management Studio Express, or Express with Advanced Services, and want to add the complete SQL Server Management Studio feature to your Express instance, do the following:

Step 1: ...

It seems that there is not a way to just update my existing instance with the service pack, but I need to uninstall everything and re install.

Am I wrong?

Service pack should be delivered through windows update. Make sure you select in the settings section to also include updates of other Microsoft products.