usually there is an update link on the right hand side of the OAF Page you mentioned (System Administration, Concurrent - Programs)
from where you are taken to an updateble page. In this page You can go exactly to Request Tab where you can modify Operating Unit
Mode from Single to multiple.
When a concurrent is designed to be of type "Multiple" then SRS Form enables Operating Unit Parameter automatically, so that you
are able to enter a specific operating unit.
E.g. Payables Open Interface Concurrent is designed as "Multiple", so if you have access to payables responsibility, you could see
how it looks like.
If your OAF Page for Concurrent Program Definition is missing update link, then it might be a security issue (e.g. the function may
be disabled for your user).
1.)To run the custom program, you need to add it to the request group of the corresponding application (Sys Admin>Security>Responsibility>Request)
Once added all the responsibilities of the application which have this Request Group assigned to them should be able to run the custom program.
2).To achieve single/multipleOU access, you can adda a parameter of operating unit while defining your custom program.
If the responsibility used to run this has access only to a single OU (no MO: Security Profile), then a single OU will be used.
If the responsibility used has multiple OU access, the OU parameter while running the request will give an LOV where you can select the correct OU.