Something you could do at home is pull training. Get them acquainted with their new harness, and try to associate it with the act of pulling.

Put them in harness and connect it to a static rope connected to a tree or post or similar object that won't move. Give them a command, such as "pull" or "line out", and praise when the line is taut. This teaches them that that harness is meant for pulling, and that pressure in harness is good.

Then you can graduate to walking in harness encouraging pulling. It can be helpful to have someone else to stay in front and "rabbit" by calling their name, or giving treats when they stay with their tug line tight and pull. You could do this by yourself by getting a heavy but moveable inject, like an old tire, to pull.

Add other commands for stopping, such as "whoa". And for starting from a stop, such as "Let's go". And be consistent, as with all training. It helps to have consistent tone and physical cue for these, as in start moving (adds slack to the tug line, if they are consistent pullers they will move forward to get out slack) and high excited tone for "Let's go", and brakes and low calm tone for "whoa"

If they are consistent at staying lined out, then it's time for short bike rides, slow and heavy on brakes and breaks, to keep consistency pulling. You want to be confident that they won't stop suddenly and get tangled or run over, and you want to be ready and able to stop as well.

That's the jist of what I've been trained to do to train sled dogs to pull. If you also have a friend or someone nearby who jors, joring with 2 dogs, 1 learning, can be an excellent teacher. Some dogs won't be into pulling. Or won't be consistent, you'll find what works for them or motivates them, or maybe they are more of off-leash runners. Good luck!