The best experience is to make an actual Lemmy account (try lemmy.world or lemm.ee) and use an actual Lemmy client.
However, Lemmy communities are represented in Mastodon as Mastodon users. (“It’s ActivityPub all the way down.”)
To follow this community from Mastodon, search for “@nerdygurdybuilders@lemmy.sdf.org” in your Mastodon client and click the follow button just like you were following a regular Mastodon user.
Replying to the Fediverse URL of Lemmy posts/comments from your Mastodon account should show up in the Lemmy community as a comment.
To create a new top-level community post via Mastodon, make a Mastodon post and @-mention “@nerdygurdybuilders@lemmy.sdf.org” at the end of the post. The first line of your Mastodon post will become the Lemmy community post’s title.
Additional details about cross-participating can be found here: https://vijayprema.com/using-lemmy-from-my-existing-mastodon/
