How do I create this "set" node?

Sorry if I’m not doing this correctly, I’m new to both this forum and Unreal Engine. I’m trying to create the node in the picture but I’m not sure how. I’m sure its very basic but thank you for your response anyway.

Well create function, or event and add it a parameter, that parameter would set thaat value, you could try the right click and collapse function .

What’s shown in the image is basically the process of setting a value to a variable. So first you will have to create a variable of the required type (probably Material for GridMatREF) in your blueprint. Once that’s in order, just right click and type in Set VariableName and you should be able to add the node.