Hi Iris,
Welcome to Blackhatworld Forum!
Read Forum Rules, Newbie Guide you will find lots of useful information about how things work.
How to private message ? If you want to start a direct message, you need to have at least 15 posts, otherwise you will not see the option to start a new direct message. Make sure your posts are good quality and do not make short, spammy or low-quality posts just to boost your post count - these posts will be deleted and your account may be banned.
For more information : https://www.blackhatworld.com/seo/why-cant-i-start-a-direct-message.1040781/