I'll do my best to help. The two games you've highlighted may be the only two games that are that are recruiting at the moment. The way to join is to click through on the link, read the information there (normally the first post has pretty much everything you need) and post interest there.
Then you'll need a character idea, and to post an idea of what you want to play. Potentially this can be as little as 'a gnome cleric' or as much as a page of background about how you grew up raised by celestial pigs and want to talk to the DM about creating a new Mud domain.
If you click through the link for Keeping the Blade, by example, you'll see examples of this. The other place you might think about for a game is
Living Enworld, the Enworld Persistent
PbP games. Information for creating a character there is in the
Official Character Thread - the first post in that thread.
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