How can I see my iMac photo albums on my iPhone after turning on iCloud Photos?

Before I turned on iCloud, I had specified several albums to be synced to my iPhone. It was a very useful feature. But now that I'm using iCloud, I can't see them anymore.

I've looked at "shared albums," but that's for sharing with other people. And when I start to set it up, it asks me to start a whole new album. I already have albums to sync with my iPhone. I don't see a way to sync them, or even see them on my iPhone anymore. I don't want to have to recreate all these albums manually.

How can I see my (formerly) synced iMac albums on my iPhone?

[Re-Titled by Moderator]

Original Title: I just turned on iCloud. How do I see my iMac's albums on my iPhone?