Hello Jack and welcome to the forum.
Self-publishing is obviously the easiest route, though not the least expensive! I self-published a small collection of poems to mark Nelson's 250th birthday last year and can thoroughly recommend the company I used. If you are not in the UK, I am sure you will find companies offering a similar service, but check them out carefully; there are a lot of sharks keen to take your money.
If you want to get a publisher to handle your work, the following link gives good advice. The question here is about publishing symphonic scores, but the process they advise would be the same for your Ode to Nelson.
http://answers.yahoo.com/question/index ... 332AA9Dc5t
Getting anything published in the current climate is difficult but don't give up. One piece of advice I will give you (I've had articles, short stories and poems published, but not music) is NEVER EVER sell your copyright. If a publisher asks you to agree to sell ALL RIGHTS, run a mile. That means the work is theirs and they can do what they like with it. Imagine then if they allowed your Ode to be used, say, as a background to a blockbuster film of the Napoleonic Wars, they'd get the royalties and not you!