English grammar does not always require prepositions in such cases. Indeed, if you included any it would seem unnatural. On the other hand, if you phrased it differently there might be prepositions.
I'm busy doing homework.
I'm busy with homework.
I could use your help getting the tire back on the car.
I could use you help with the tire change.
Basically, help doesn't require such a preposition when you use a gerund-participle to describe what the help is with. In one analysis, they are adverbials - but not all adverbials use a preposition.