When I click sqlservr.exe, this message appears

I installed Microsoft SQL Server 2012 LocalDB.

When I click sqlservr.exe, this message appears.

Could you please help?

Thanks

I don't think double-clicking the SQLServer.exe is the way to start a LocalDB installation. See here for a primer.

what is the easiest way to start a LocalDB?

From the link I posted in my previous response:

SqlLocalDb create "MyInstance"
SqlLocalDb start "MyInstance"