Adding Text and lines to a video

Hi , I'm about to edit my first video.

I want to add some text and lines to the video as shown in the picture below ( 1+2) , where I'm editing a picture.
Adding 1 after some 20 sec , and 2 after some 30 sec.


[Attachment 50382 - Click to enlarge]

In this case, I was using a screen recorder , using the MKV format.

What video editor should I use , and how am I doing it ?
I prefer freeware.

If wanted I can upload the video

Thanks :)