Hey Bonfi64,
I run Cubase, But most of the process should be similar, First to use the ARP as an effect you need to have the correct .DLL files in your VST folder. There are two .DLL files for the ARP, the first ARP2600V2.DLL is for runnung the ARP as a VSTi (instrument), the second ARP2600V2 Efx.DLL is for running the ARP as a VST effect. Once you have these in the correct folders, you should be able to add the ARP as an effect to your guitar track. Check the ARP manual sections on the pre-amp input and the envelope follower. Hope this helps. Have fun!