Without an optional Analog I/O Extension module installed, the ABB ACS800 VFDs provide three on-board analog inputs; one is a voltage Analog Input AI1(RMIO board X21 connector, terminals 3 and 4) 0/2 - 10vdc and two 0/4 - 20mA current Analog Inputs RMIO Board X21 connector, AI2 terminals 5-6 and AI3 terminals7-8 respectively.
If you intend to use a 4-20mA analog speed reference, wire up the 4-20mA Source to RMIO board X21 connector terminals 5(+) and 6(-) then "tell" the VFD to "follow it" by setting P11.03 to "AI2".
In order to Start/Stop and change direction of the drive you will have to provide at least two switches (dry contact relays): "pick-up" the 24vdc (+) wire from the RMIO board X22 terminal, connector 8 and run it to one side of the switchs (relay contacts); the "other side" of switch (relay contact) designated as Start/Stop will be "returned" to RMIO X22 connector, terminal 1 as DI1 and the "other side" of the FWD/REV designated switch (relay contact)will be "returned" to RMIO board X22 connector, terminal 2 as DI2.
Once accomplished you will have to "tell" the drive to "listen to DI1 and DI2 by setting P10.01 to "DI1,2".
Start/Stop Switch OPEN -> Drive Stopped
Start/Stop Switch CLOSED -> Drive Started
FWD/REV Switch OPEN -> Drive to Run FWD
FWD/REV Switch CLOSED -> Drive to Run REV
Be careful though, with this setup (one Start/Stop switch), after a fault reset the drive will start if the Start/Stop switch is CLOSED.
This is a "bare-bone" setup but will get you going; I know the manuals are translated from Swedish by a Swedish speaker; try studying though, you'll eventually get the idea...