Most video software will give you somewhere the HTML code you need to paste.    If videos are stored someplace like photo bucket, you'll see several selections to choose from like IMG code, Direct link etc.  

1. Choose: e  "HTML" code and copy it.
2. Then in your post here click on the "Source" button on the very upper left corner of the tool bar. If you don't know much about HTML code then just know you will see a version of your post with a bunch of extra symbols and stuff.

3.  If you are not used to HTML code, then just scroll down past all of that and paste the photo HTML code there. 

4. Then click on source again and save.   Your video should appear.

You can try just paste the HTML code without getting the source version.  Sometimes this works and sometimes it doesn't.  Don't know why.