Without seeing our layout, and what valves, controls you may have, it's tough to give specific instructions. If there is a vent high up in the system, you'd put a hose on it, run water through the system from the system fill valve until it doesn't show any bubbles. Close that drain valve and pressurize the system with a little bit more water until it reaches design level (usually around 12-14psi), then shut off the fill. If you have an air extractor, it should work out any air that is left. If you don't, it gets more complicated. Note, potable water will have some dissolved air in it, and that will need to also work its way out of the system, and might require a small addition of water to top things off in a day or so of running.
Does the boiler try to turn on and fails? Does it not try to turn on? It may be you need to press a reset, or some other interlock is not closed (like low pressure).
Without more symptoms, can't give you better help. The operator's manual typically has some troubleshooting help in it. Have you tried that? That should be your first step to isolate what's going on. It may also have a theory of operation, which may also help you figure out what's going on. If that is beyond you, you may need to call in a professional, or provide some pictures so we can see what's going on.
IOW, a bit more help from you on what's going on will provide better help from people on the forum.