First, you'll need to compile the gtfs-realtime.proto file into a library that can help you produce data in the binary protocol buffer format (the .proto file itself isn't the data that is exchanged between a producer and consumer). More here on this process:
Alternately, you can use the existing gtfs-realtime-bindings library, which has already done this step for you for several programming languages:
When you've done this, you'll need to write code to instantiate a TripUpdate with the TripDescriptor.route_id set to your route, and the TripUpdate.delay set to your delay value. Note that some consumers may not support this format - typically delays are created at the trip and stop level.
There are a number of GTFS-realtime demo apps here that might help you get started: