Hi Francisco,
Word can't do that automatically. You can do it manually by selecting the text that should be in two-column layout and using the columns tool to change it to two columns. I could give more detail, but you don't say which version of Word you're using.
Do be aware that applying a two-column layout to a block of text may change your document's pagination. Also, if you send the document to someone else, the pagination might well be different if they're using a different printer than you use.
Cheers
[MS MVP - Word]