Creating a screencast is easy - all you need is a steady hand and a lot of patience. If you want to help out with Plasma HowTo screencasts, here are some guidelines:
Use a resolution of 640×480 to produce GIF files with the same dimensions as the original screencasts.
Make your desktop look like the ones in the other screencasts. This includes panel height, widgets, desktop style, icons in the system tray and wallpaper.
Hint: Most are default settings. I've increased the panel height slightly to make the system tray look nicer (shows both top and bottom borders).
No unnecessary mouse movements. In the beginning and at the end the mouse pointer should be completely still.
Smooth mouse movements, not too fast. When clicking it's sometimes nice to hold down the button a little bit longer than usual before releasing.
Use left click when possible.
Redo until you're 99.9 % satisfied.
Follow the name convention: Plasma_howto-[section]-[item]-[version].png. See the name of the other screencasts.
Edit the GIF files with an image editor that support animated files, such as GIMP. Change the first frame to 1000 ms and last frame to 3000 ms (make sure there aren't any too long frames before this one).
I am not sure I understand the purpose of the link in Unit 16. The mention to UserBase seems to refer to to the site as a whole, so I am not sure a link to the front page is particularly useful. Anyway, it we need a link I would suggest something, that can be easily translated like fx Special:myLanguage/Welcome to KDE UserBase.