On a standard instrument, you would finger the C with one little finger, then trill the Db (C#) with the other. On an Albert, I don't think that the mechanism allows this one, but it's been a while since I've played an Albert. On an Oehler, the Patent C# mechanism should allow you to finger the C with the right hand, and trill to the Db (C#) with the left.
This is all from memory, by the way...