To create a thread click on the appropriate board. There is an orange box at the top right saying "Create Thread". Click on this and then fill in the subject line and the text, adding extras if desired from the choice along the top. Then click on Create Thread at the bottom right.
To reply to a thread either use the Quick Reply box at the bottom of the thread or, to add more features, click on the orange Reply box at the top right of the Quick Reply box. When you have added your text click on Create Post at the bottom right.
Somewhere in another universe, dear brother, you got saved.