with this plane .... if so, could someone be kind enough to reply with a 'Howto' ??????

What are you trying to do? Which simulator platform?

Sorry Henry ..... a bit sparse in the detail department ..... just recently moved up to P3d v4.1 ..... and am disappointed with the lack of gear/flaps/switches etc. sounds with the Do228 package .... in my travels around the forums I often encounter references to the Doug Dawson gauge where installing the Realair Duke & Legacy in recent versions of P3d wipes out these type of sounds which are audible in FSX installations ... DD's gauge apparently miraculously brings them back to life ..... his gauge has been around for a while, but there's currently a 64-bit version about, which of course will only work in v4 .... it was the possibility it might do the same for the Do228, and if so, anybody got it to work??? that's it in a nutshell .... Alan

Check out this post. I have successfully converted a dozen or so aircraft to P3Dv4 by doing this procedure. The screenshot assumes you are installing the aircraft in the P3Dv4 folder similar to earlier P3D and FSX sims. I don't have the Do-228 so there may be other accommodations needed.

https://www.avsim.com/forums/topic/525550-iris-sale-in-bargain-hunters/?do=findComment&comment=3760583

I used a replacement engine for the DO-228 with FSX:SE, and preferred it over whatever it is that god awful stock sound from Carenado is.  The replacement engine sound changes with RPM (the stock engine sound does not), and it sounds better too.  Technically, I think it's actually a jet engine, but it works.

I migrated to P3D with a new computer, and don't have the replacement engine for the DO-228.  And unfortunately, I think it's been removed from the library here.  If that's not incorrect, please link me to it.  Thanks.