Hello. I think you mean to say how do I apply to jobs that I want to do? The "heart" is just to save a job that you like so you can easily access it when you are ready to apply. But don't wait too long as some clients will hire within 1-2 days of the job advert going up.
To apply to jobs you "heart" (like) then you have to write an application letter, just like in the real world, pay the connects needed for the job (think real-world stamp and envelope), and send your proposal.
You can learn more about how everything works here at: https://support.upwork.com/hc/en-us/articles/211062998-Submit-a-Proposal
If I have misunderstood your question, I apologize.
submitting work that i would like to do is that just to heart the position? what else do I have to do?