Hi Fiona, and welcome to the forum.
A good source or information is
NATIONAL ELECTRICAL CODE BLUEPRINT READING.
It has blueprint type illustrations with code references so it's meant to be used in conjunction with a code book.
You can also go through archived electrical plans and learn something there if i understand your question correctly.
For online courses i've heard good things about Bluevolt.com but i can't personally vouch for them. (Has anyone else heard about Bluevolt?).
Good luck,
Zero
