In Aligner, choose File | Open, and select your plain text file.

 

and you may see this sort of thing in Sentence view,

 

 

or in Paragraph view,

 

 

Edit it, as necessary, e.g. splitting or merging paragraphs or sentences. There's a taskbar with buttons to help above the text.

Ensure the language is right:

 

And save it as a .VWR file:

 

.

 

See also: example of aligning