You might find yourself in the unfortunate situation of having your SSAS server within a particular domain but your client machine in another. Since SSAS only supports Windows logins it is necessary to connect to the server using one (it is possible to connect anonymously but I am not addressing that scenario in this post). The two commands below will allow you to launch SQL Server Management Studio and Visual Studio (BIDS or SSDT) using a Windows account from a domain other than the one your client machine is currently on.
SQL Server Management Studio 2012
>runas /netonly /user:domain\username "C:\Program Files (x86)\Microsoft SQL Server\110\Tools\Binn\ManagementStudio\Ssms.exe"
Visual Studio 2010
>runas /netonly /user:domain\username "C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\devenv.exe"