The ABB website,
www.abb-drives.com has the Instruction Manuals you need. Or, if that doesn't work, send me your email and I will send an electronic copy.
Briefly, to enter the software from the standard display, push the parameter button PAR. That takes you to the group level. Use the double arrow keys to scroll around the groups until you find the one you want. Use the single arrow keys to scroll around the parameters in that group. Press ENTER to open a parameter, make the desired change, and press ENTER again to save. Pushing the double arrow keys will always move you from group to group.
When you are done, you can just wait and, after a couple minutes, the display will time out and return to the standard display or, simply press the actual key ACT and you will be taken back to the standard display immediately.
One word of caution. While it is not hard to get around in the software in this drive, it would be unfair to claim that this drive is easy to program. The ACS600 and the newer ACS800 are go-anywhere, do-anything-well types of drives and there are plenty of places to go wrong. A little training would go a long way toward a satisfactory operation.