To start the schedule in the GUI mode simply select theExecute button on the tool bar or the corresponding Script->Execute menu item while the schedule is opened in the Scheduler tool. Once the schedule is executing you may use the Stop and Pause buttons to stop/pause the schedule. When there are both the schedule and a script opened in the GUI the Execute button always prefers the schedule. To execute the script alone, right click the script editor and select Execute script from the context menu.
As the GUI is not capable of executing scripts in parallel it will always execute them sequentially (one at a time). For parallel executions use the CLI or Java API execution mode together with the -n/--nodisplay option.