Hi,
We need to first create account on prestashop addons market place ,validate module using module validator ,create good screen shots,documentation and demo instance to publish module.
Forum account and addons store account logins are different.
There is option in menu to go in seller account.
PrestaShop Tutorials Videos [How to do Tasks]
https://www.prestashop.com/forums/topic/907438-prestashop-tutorials-videos-how-to-do-tasks/