If you want to append a file at the end of the file you are working on in the buffer, enter:

r filename

Or, if you want to read a file in after a specific line in the buffer, enter:

nr filename

where n is the number of the line in the file.

To display the contents of a file in the edit buffer, enter:

,p,

On your screen, each line of the file is displayed, for example:

 
,p,
Oh, you better watch out
You better not shout
You better not cry
I'm telling you why
 

Once you know the line numbers, you could insert the file scrooge after the line You better not cry. Thus, you would enter:

3r scrooge