Paste addresses separated by blank lines, choose the label grid and font size, and adjust the offsets if your printer runs off-centre. Check the preview, then print.
The 3x10 grid matches Avery 5160 and L7160 style 63.5 x 38.1 mm labels, 2x7 matches the larger 99.1 x 38.1 mm sheets, and 2x5 suits shipping labels. Always print one test page on plain paper and hold it against your sheet before committing.
Printers vary by a millimetre or two in how they grip paper. Use the horizontal and vertical offset controls to nudge the whole grid, and make sure your print dialog is set to 100% scale rather than 'fit to page', which is the usual culprit.
Yes. Enter one address and turn on repeat, and it fills the whole sheet — the standard way to make a page of return address labels. Otherwise separate each address with a blank line to place them one per label.