By the way, when pressing B, then selecting an image, it selects only one — cannot select two or more in the Print Module page.
No. You make your selections in the Library module. In Grid view, you can select individual images by control-clicking on them, or a strip of images by clicking on the first one and then shift-clicking on the last one. You can also do this in the filmstrip.
If you click on an image or series of images and then press 'B', it adds that image or images to the Quick Collection. You can then click on the Quick Collection (in the left pane of the Library module) and then go to the print module. This is handy if you're planning to print a series of images from different folders, without having to worry if you're control-clicking and keeping the ones you want. If all of the images you want to print are in the same folder, you don't need to worry about creating a Quick Collection.
If I'm not being clear, this is the procedure. Let's say you want to print a collection of images from different folders. Go to the Library module and select the grid view. Click on each image (or shift or control click on a group of images) you want to print, and press 'B' on the keyboard to add that images or images to your quick collection. Alternately, if you mouse over the image and you see a small circle in the upper right corner of the image, clicking on that circle will add the image to the Quick Collection. Setting that up is under View Options, but that's getting off topic.
So, you've gone through your folders, selected the images for printing, and added them all to your Quick Collection. In the left pane of the Library Module (under 'Library' and just below 'All Photographs' is 'Quick Collection'. Click on that and it will show you the images you've added to your Quick Collection. If those are the images you want, then go to the Print module.
In the Print Module, click on Page Setup (at the bottom of the screen) and select 'A3' as a paper size. Now in the right hand panel of the Print module under Layout you set up your cell size (the size of each image), the spacing between the cells, the page margins, the numbers of rows and columns (2 columns in this case), etc.
Hope that helps...
Mike.
P.S. A Quick Collection is not intended to be a permanent collection. It's something you can empty and refill with different sets of images. If you've added a group of images to your Quick Collection and think you may want to use this same group of images again later, you can create a Collection of those images (in the Library Module) by right clicking (Windows) or control clicking (Mac) on where it says 'Quick Collection' and selecting 'Save Quick Collection'. Your Collections are stored farther down the left panel in the Library module, underneath 'Folders'.