Translated literally, 'mettre la main à la pâte' means to put your hands in the dough.
The expression, which dates back several centuries, normally refers to one of France’s most beloved professionals: the baker.
If the baker doesn’t get their hands in the bread dough to knead it again and again, there won’t be any bread to eat and the consequences would be dire.
In this sense, mettre la main à la pâte means to participate in the work that has to be done, to get to work, or to get involved (often in a difficult or tedious task).
In English we might say ‘to roll your sleeves up’ or ‘get your hands dirty’.
Over the years, the expression has also taken on the meaning of showing support, or even helping others by getting something done especially if they have a heavy workload.