Jehu organized a massive, highly public event dedicated to Baal. The primary approach among commentators is that his order was a call to prepare the people, send out invitations, and designate a specific day for this gathering. Building on this, [מלבי״ם] explains that the goal was to establish a genuine festival. This would be a formal holiday where all ordinary work was strictly forbidden.
The plan required a vast gathering of the population. The masses were expected to halt their daily routines and assemble in one central location, crowding inside and around the temple of Baal. This directive was quickly put into action. A formal declaration went out to the public, officially setting the date for this great holiday and assembly.