Once you have completed the settings of your Dynamic Search Campaign, and then defined the target channel, it is time to 'submit' or 'run' the job.
Use the play button to manually run a job ()
Use the submit to file feature as a test run in order to double check that the keywords, ad groups and ad copies you set up were created to your satisfaction. It is also a good tool to review if keywords were created that don't make sense, or words in you ad Copy were cut off in a manner that is not good for your campaign etc.
It is a best practice to submit your campaign to file before submitting the campaign live, and therefore making changes in your target channel. It can be messy to fix the campaign settings after they are already in your marketing channel.