How do I open a grouped node tree?

Hi community! I have a graph that I've dowloaded from the web. And I want to change some nodes inside of it. The thing is, right now I can see only one node with all the inputs and outputs on it. (I called this one a group. Perhaps it can be a seperate graph). How can I open this graph within the SD (without searching it through folders) to see the whole tree? (never worked with the grouped nodes in SD)