Subscribe to the communities you want. I usually do so by visiting one directly, like https://lemmy.world/c/technology. Once there, the sidebar has a button for it.
Go to "communities", select "all" and search for the subreddit equivalents you want. Then you can subscribe to them - their posts will be visible when you browse by "subscribed" on the main page. "Subscribed" is basically the equivalent of "Home" on reddit.
I’m getting older, so my speed at picking up new tech is a little slower than it used to be, but I’m finding my footings.
From my limited interaction so far, I think what also happens is that there are lot’s of different servers to connect to, and each server can have it’s own “sub-reddit” which are called communities.
For example, lemmy.world might have a “showerthoughts” community, but another server like “sh.itjustworks” can also have a “showerthoughts” community. When you subscribe to a community, you subscribe to that servers instance… so depending on which server community you subscribe to, might not be the most active one. at least that’s how I have pieced it together. Please someone correct me if I am waaaaaaaay off!