Newbie's basic keyframe question
Apologies in advance for what is probably a spectacularly obvious question, but I'm really confused here. I'm a graphic designer trying to turn a layered Photoshop file into an animation, and I'm getting stuck at what is probably a really basic first hurdle 😞
I understand the basics of Animate, in files created by an external expert I can move stuff around, do the tweens I want, export successfully etc. The only thing I can't work out is how to turn my layers on and off when I want.
When I import my Photoshop file, all the layers are present and correct, and all of them are visible. By default, the timeline starts with every layer as a (black circle) keyframe. However, I don't want all of the layers on at the beginning, and some need to come on and off a various points later. So I convert all the unwanted layers' keyframes to blank keyframes to turn them off at the start. But then if I try to insert a keyframe at the point I want them to come on, this new keyframe is also blank, and seemingly won't convert to a normal keyframe. So basically I can't turn my layers on again when I want.
I've done a lot of Googling and also watched the Adobe tutorial about keyframes but I'm obviously missing something really basic that everyone else knows and I don't! Can anyone help please?
Thanks,
James