Online Audio Course
I've just done these 2 courses on udemy
Quite basic but if you are just starting they are pretty good.
The second one gives a good explanantion of how to use REW
They have a deal at the moment if you sign up to both at the same time
It's £19.99 in the UK, not sure about everywhere else
I found it very useful, especially the second part with the REW tutorial.
There is a third part about crossover design, but thats at £99.99 at the moment.
Im watching to see if it goes down at all