I have done this connection with a PowerFlex drive over EtherNet/IP. I don't recall the actual drive model, but I can check after the new year. It was not straight forward - the EDS file did not work and the drive actually used the 4-byte run/idle header (usually only the scanner/PLC uses this).
Do you have an updated EDS file from Rockwell? If so, add it to the DTM config in Unity and add the device. Set the options - EDS file dependent - like data sizes and RPI that you want, then finally the IP address.
This is a rough outline - exactly what isn't clear when setting this up? The user manual has some stuff, and I can provide screenshots to steps that are troublesome. Anyway, get started and let us know where you get stuck.