purchase requisition settings in ECC & gATP to do a.check in gATP

Hi Experts,

How can I check the availability check for purchase requisition (ME51N) in gATP.

Can anyone please help me what are all the settings required to do availability check in gATP for purchase requisition.

I know the settings how to do for the purchase order availability check in APO but not sure what settings are required to do availability check in gATP for purchase requisition.

Please..

Thanks..