You could do one of two things:
If you think the premise is really that great, look over it, learn more about story structure and rewrite, then set it aside and write a new spec
If you believe everything is tip top, set it aside and write a new spec.
You may want to produce your screenplay, get it out to agents, ect. Ect. But if you dont have a ton of money just lying around you wont be able to do it without a studio's help, and if this is your first feature, you're going to have a bit of trouble find support
I'm not saying you CANT do it by yourself. You could get craigslist actors, watch endless YouTube tutorials on film making and buy your own gear but it's best if you have a studio or some kind of agent backing you for a feature. The process sucks but it's all about learning!
Hope you make something you're proud of!