Help me out here about posting in any Rp forums.

[Solar Bolt 17]

My Favourite Mane 6 Pony

rainbow-dash

How did you find MLP Forums?

Google

How you became a fan of My Little Pony

A friend of mine.

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How do I post in the forum thread or any Rp forum threads such as the one for A Casual Stroll? Or do I have to do a Rp thread that's open to start a conversation in with those bubble things? Help me out here please somepony.

[Snow 5,305]

Welcome to the forums @Solar Bolt 
First and foremost you need to achieve the rank of muffin which is 5 posts, to do so simply post in threads in sections like Show Discussion, General Discussion and Sugar Cube Corner.
That will give you access to the RP sections, from there it is no different to posting in any other thread, except of course the minimum character limit (200) for each reply to an RP for quality sake.
By following these reminders and hard to see highlighted prefix legend's you cant go wrong. 

[Rikifive 23,472]

Hello and welcome to the herd!  

[Totally Nyx 35,455]

Hi @Solar Bolt. Since you've already made a welcoming topic and this post is asking about how the site works, I've shifted it over to the Site Questions & Tech Support section. Have a nice day.