OK I've gone ahead and added a video for that section. In your case, instead of clicking the planar projection, click the Cyllindral projection mode or whichever makes it easier for your case.
Alternatively for your case you could simply apply an Unwrap UVW modifier, and at Map Channel choose 2 and on the options choose Move instead of Abandon. This moves the object's existing UV mapping into UV channel 2. This might work out better for you.
It's also possible to use the UVW Map modifier to quickly unwrap your UVs.