Ok, here's what you should do step by step.
1) Open your movie maker and click on "Import Media"
2) Select whatever video you want to use on utube
3) Right click on the video and select "Add to timeline" or hit ctrl+d
4) Click on titles and credits.
5) Click on "credits at the end"
6) Type whatever text you want them to read
7) Down, you'll see more options. Click on "change the title animation"
8) Scroll up and select "basic title" (Text appears with no motion or fade"
9) Click on "change the text font and color" you can make the background black here.
10) Click on "add title" once finished.
11) Now if you look at the timeline, you'll see your text at the end of the movie. If you hover your mouse, you'll see it says "click and drag to trim the clip". If you drag it to the right, it will increase the duration of your text.
Enjoy.