How do I set up a radio as a repeater

I am going to use digi xm-x9-3p-u radios. I need to communicate from one location (MTU) through another (Standpipe) location to a 3rd location (Booster pump station). The mtu will need to be able to poll the standpipe and the booster pump station. There will be only one radio at each location. I was hoping there is a store and forward that could be set up at the standpipe. The standpipe is geographically between the MTU and the booster pump station. There is line of sight between the MTU and the standpipe. There is also line of sight between the boosterpump station and the standpipe. There is not line of sight between the MTU and the booster pump station. I hope this is enough info to explain my situation. Thanks in advance for the help.

By default it is already enabled. All you need to do is place it in range of both other ends. Also make sure that on the other two ends that the TO command is still set to C0.