重载赋值运算符以在后缀表达式解析器树C ++中使用

I had a question regarding this same program a few days prior, but now I'm stuck at a new problem. My instructor told that I need to overload my assignment operator to allow my constructor to understand assigning one binary tree to another. I've tried several different efforts, but can't seem to get the right syntax or idea down. I've spent an hour digging around on Google and can't seem to find any examples close enough to what I'm doing to really help me. The way he spoke, it seemed as though overloading the operator would be enough. Every example online seems to use overloading AND a separate function. Any thoughts?I had a question regarding this same program a