How to approach seed funding?

I built a product last year to fulfil our own need within a charity that I am the founder of - a fully customisable events platform built for WordPress. We've since gone on to have more than 20,000 registered attendees through it, delivering events of various scales from 50 to 3,500+ concurrent attendees.

It's received incredibly positive feedback, and so I'm at a stage where I'd like to turn this into a salable product for others to access. Here's the rub... it needs further development that's beyond my skills and marketing beyond my budget.

Seed Funding seems like a sensible route to investigate. However, I have no experience in this. Any advice, no matter what, would be greatly appreciated?