I have a sample. I have the idea, just no clue hoe to execute it. Someone please help me figure out how to get to start.
That depends: you can either add a sampler node or multi-sampler node, and control that from a melody source (like a piano roll node), or you can use an audio file node and manually arrange your audio file on the timeline (by default, it'll be played at the start).
In both cases, you continue by connecting the sampler node, multi sampler node, or audio file node to an audio destination node to produce audio output.