One thing the guide does not tell you how to do; Find out which city has off world transport.
From your travel screen, select planet to view all of the cities. Look for a city that looks like this;
Now that you have a desired destination, you should look for the NPC who can rent you a speeder, cross terrain travel on foot will take forever.
Once you arrive in the city you will find the NPC who can arrange your passage off the planet inside the starport.
If you have not selected a faction or group to join, you should do so. There are also a couple groups that offer to rent you a ship to use. You have a limited amount of starting funds, purchase your passage off Corellia wisely or you could find yourself on another planet with no way to leave.
Edit - minor spelling errors