1. Go to Format->Columns.
2. Select the number of columns you want
3. If you want control over what text goes in which column, uncheck the "distribute text freely amongst columns" box.
4. Hit OK.
5. Now the bit that took me five minutes to work out (Openoffice help sucks): if you want to put text in the second or subsequent column, you can't just click there - you have to go to Insert->Manual Break... and choose "Column break".