Have you followed Presonus directions in Studio Ones manual?
If you have downloaded and installed the manual, then you can find in Studio One at: Help/ Studio One Reference Manual/ Setup/ Set up your MIDI devices
Arturias keyboards needs to be set up as New Keyboards as they are not in Presonus set up menu.
Your keyboard need to be connected to your computer, then it will/ should be availble in the "Recieve From" and "Send To" drop down menus in Studio One at: Studio One/ Options/ External Devices (Add/ New Keyboard).
Be aware the Filter check boxes shall be left unchecked unless you wan't to disable features. Some make the mistake to think they add the feature if they check it.
In addition to this - follow Studio Ones manual to set up your device.
Here is a video that show this among other things:
https://www.youtube.com/watch?v=1ucsgZF5L5MI use another keyboard, but the procedure should be the same.
If you have setup your keyboard this way, and you mean you wan't to map your keyboard for Presonus Control Link feature, then it's another procedure.
BTW. There
Hope this helps.