A LyX conference poster template for members of the Maxwell Centre, Cambridge
Navigate to Document > Settings > LaTeX Preamble. In the first 4 lines of the preamble you can set the text you wish to appear in the bottom left and right corners, the paper size (either A0, A1, or A2), and the number of columns (either 2 or 3). Font sizes for each paper size can be changed at the bottom of the preamble, but the defaults should suffice. The template comes with 2 columns-worth of content by default. If 3 columns are desired, simply add another column in the main body of the text (i.e. add a collection of fblocks flanked by \begin{fcolumn} and \end{fcolumn}).