If you are just going to type in your description, just type it in the Description
Field:

If your are, for example pasting text from a .NFO file, usually
you find that there are a lot of extra characters in the text. This makes it undesirable
to have it like that in your description. For example, a .NFO file could have the
following description:

To fix this up in Vanilla, simply select the relevant text and paste it into the
Description field:

As you can see, the description has a lot of ugly characters in it. To fix this,
just press the "Clean Up" Button:

and, Vanilla then cleans up the text as:

All you need to do is join up the paragraphs, and away you go!
If on the other hand, you have a large amount of text as your description, but you
find that the Description field is too small, there is another solution. Simple
press the "Expand" Button:

This will bring up a new resizable window. This window you can resize to whatever
size you require. The windows will look like:

There are a few buttons on top of this window:
Clean Up - Does the same as "Clean Up" in Path #1.
Paste - Pastes the current contents of the Clipboard to the Description.
Clear Text - Clears the Description
Cancel - Closes the Window, but you will loose all changes since this window was
opened
Save Changes - Saves what you've added to the window, and returns you to the Add
Record Screen.