I have in scene a character which loops che same animation over and over again. I need to swicth his material when his animation reaches frame 37 and swich back to its original material on frame 75. I already created the notifies, but I have to clue how change the material using the AnimBP.
Same as you would anywhere else. You just need to drag off the pin from the character cast. Possibly select the mesh before searching for material nodes.
Sorry I don’t get what you said. From the AnimBP I can’t find any material nodes, I just have “Try Get Pawn Owner” and “Event Blueprint Update Animation” nodes, but I can’t find any node by dragging those pins that affects the material. My purpose is to make the character invisible when the animation reaches frame 37, so he has to change its material (which I already created) to a refractive one. I’m a bit noobish on blueprints since I’m mostly an artist 
easiest way if you can’t figure out how to cast - get the notify to set a bool on the character. use the bool on the character to make the needed changes.
Actually if you want to be good about it, create a custom event on the player and call the custom event from the notify.
Thank you!