How do i transfer data?

I have made a system that opens a GUI and then manages some things... I have the script that senses when a block is touched, and then fires a remoteEvent to the starterGui, then i have the script that can tell if you press yes or no, and now i need my script to manage the purchase if you press yes. However, in that script, i need to know the username of the person who pressed the yes button, and i dont know how to tell it that.

(to clarify, the sensor script is a serverScript, the Gui button script is a localscript, and the Purchase managing script is a serverscript.