I am reading a recipe and I noticed that in it it says "mix to incorporate" I am baffled. What does that mean?
It means mix until the 2 things are evenly mixed, so that they are 1 thing now.
You want to just mix enough so they are evenly mixed and no more as sometimes mixing more than necessary can spoil the recipe
"Mix to incorporate" is probably read like "mix it (so that you'll) incorporate it" where incorporate means to "add in".
Incorporate: "make into a whole or make part of a whole; "She incorporated his suggestions into her proposal""
Simply means that you want to get the ingredient that you are mixing to incorporate (or set of ingredients) evenly distributed with everything you've added already.
For example you might be asked to "incorporate" the ingredients for a scone, but because scones take a light touch you aren't going to want to continue beating and beating them until the dough is smooth.