You can log into Omnibear using web sign-in. This allows you to verify that you own the website you want to post to. There are a number of ways you can implement web sign-in on your site, but the easiest and most common is through indieauth.com.
To use Omnibear, your website will need to support two things: authentication and micropub. These pages will help you get everything set up and ready to go. Once you have posted to your site, you might (optionally) consider informing other sites with webmentions.
If you’re not ready to set up these features on your website, consider trying Omnibear by logging in with commentpara.de and it will take care of the rest.
Omnibear posts to your site using micropub. Micropub is a web protocol used to create, update, and delete posts on your website using third-party clients (apps). It is an open specification published by the W3C along with other emerging social web protocols.