Minecraft wiki entry for Setting_up_a_Spigot_server, associated text: Double-click your run.bat in the Spigot directory. A command prompt window will open briefly, then close.
Open eula.txt in the Spigot directory, and change eula=false to eula=true, if you have read the eula and agreed to the rules written down. You can find the eula here
Double-click run.bat again to start the server. Some new files will be created in the Spigot directory.