To make a submission to Tropical Agriculture, you will first need to register a user account with the journal (see Registering with the Journal). After that, when you login, you will be taken to your Dashboard.
The Dashboard shows your the submissions that have not been published under the "My Queue" tab. The "Archives" tab shows the submissions that were published or declined.
A new submission can be started by clicking on the "New Submission" button on the Dashboard. For more information, see Learning OJS 3: Submitting an Article.
See also the submission checklist and author's guidelines.