When you’ve found someone who seems like a decent candidate so far, make first contact. (The contact form on the website is fine as a first step.) Introduce yourself and state what you are looking for (a developmental critique, copyediting, etc.). Give a very brief description of your project, including its genre and approximate length. Give an idea of your planned next step and any deadlines (even if only approximate ones). For example, have you already signed a contract with a subsidy press for publication next fall? Are you planning to submit the manuscript to publishers and/or literary agents after editing?

An edit requires a substantial investment, many times greater than the cost of a book. Editors who spent years as assistants, learning the craft of editing and acquiring the knowledge of how to guide authors, are a safer choice. Their track record speaks for itself; editors at this level have bestsellers and award winners in both the traditional and the self-publishing space.
I’m sorry you feel that way about my participation in the discussion and defending editors of similar background to myself from what I considered unwarranted disparagement. Perhaps the only approach that would have 100% proof against accusations of “trolling” would have been to allow the claims to stand unchallenged, but that did not seem fair to people who come here to get useful information.
A place you can post your job and hire freelance editors. With nearly 60,000 editors on the site, however, it can be a daunting project to find the right editor. To narrow down the candidates, you could make a detailed project description with required skills, language competency, and portfolio requirements. This should help eliminate unqualified editors. You can also include a random requirement like “Respond with ‘Hey, Jedi!’” in to find those detail-oriented editors who actually read your entire post and follow directions.
2. Copyeditors aren’t the last line of defense when it comes to a book’s mistakes. Formatting, which is done after an editor has done their job, can lead to unintended errors being introduced into the text. That’s why it’s important to hire proofreaders to comb through edited text *after* the book has been formatted for print or digital. Proofreaders are your last line of defense—but they’re human too.