The help file says there are menu options for these.
Run Menu
The Run menu includes the following commands for running the script.
Script execution can be cancelled by pressing <ESC>.
Execute Entire/Highlighted Script
This runs the entire script that has been loaded into the Editor, or the highlighted portion of that script.
Run from Cursor
This runs the script from cursor point to end of the script.
Run to Cursor
This runs the script from the beginning of the script to the cursor point.
Run Current Statement
This runs only the statement where the cursor is located.
Execute Script Step by Step
This lets you step through the script.
Step through script from cursor
This lets you step through the script, starting at the location of your cursor.
Connect
This command lets you open a new connection to an Oracle database.