Steemit itself doesn't support video content by default. However, there are some ways to monetize videos on steemit. One way to do that would be posting videos on youtube and then embeding them on steemit posts.
Here's how to do this: Upload your video on Youtube. Copy the link of the video url. Now visit Steemit.com and click create new post icon. Make a post and add the video description.
On top of the page, paste the video url. Steemit will automatically embed it. This way, you can monetize your videos on Steemit.
Another way to do this would be to use DTube. DTube is an application built on top of Steem. You can post videos on the main website of DTube and they will automatically appear on your steemit.com blog.
To post videos on DTube, visit https://d.tube (this is the official website of DTube) and login to the site using steemconnect.
Click on the upload video button on top. Fill the forms properly and upload your video. Then if you visit your own blog at steemit.com you will see a post about that video posted on your blog.
One other way you can monetize videos on steemit.com is by using Steemir App. Here's an official tutorial video about how to do this:
I don't know of any other ways other than the three I mentioned above. If you know about any other methods, please inform me about that in the comments.