Make sure that your manuscript is the best it can be and free of typographical errors. Getting published is as much work as writing the novella itself, so make sure to make the most of any opportunities you have by creating the best material possible.
Find a literary agent, preferably one who has been successful in getting novellas published in the past. These professionals have already established relationships from publishers, and also know where to effectively market your work.
Research publishers that have already published novellas, and send them a copy of the manuscript, as long as they accept unsolicited submissions. Also send your manuscript to traditional publishers, but realize that their acceptance of such submissions is very uncommon.
Look for contests and periodicals that accept novellas for submission and publication. Miami University, for instance, offers a contest that includes a cash prize and publication for the winner.
Keep trying to get your current work published, while continuing to work on writing additional pieces. As publishing a novel is extremely difficult, you must expect rejection, and many writers forget to continue to work on additional writing while trying to get their current masterpiece read.