Search for the campaign via Find campaigns tool from the left-sidebar. From the beginning, the search will be aligned to appropriate Influencers. But if you turn off the filter "Show only campaigns..." the results will be expanded.

Choose the campaign that you like from search results.

Apply to a campaign with channels by clicking Learn and Apply. After submission the message will be sent to the person responsible for running this campaign to review your application and provide feedback.

You can track booking status on the External campaign page (left-sidebar). 

Different status updates appear in the information hub on the top of the page. 

All further actions will be done by the Influencer - publication draft, posting, and confirmation of post with the brand.
Influencer agency receives the predefined share from the costs booked by the channel.