Explore Building
Learn how to Build a Driving Base if you don't have one yet
Explore the Programming
Learn programming basics here
You can use rotation or time to achieve this goal.
Example of command
Have robot move forward stop on line using sensor.
Have robot move forward, stop on line using sensor, turn around and move forward. Using Loop have robot repeat.
Add a 4 second pause
Have robot move to black line. Create loop using sensor to change direction when line is detected.