Alright . In that case you will have to remove all the old window glazing . It ' s like a hard putty . Get down to the bare wood and make sure that it is cleared away of all remnants of glass and putty . Don ' t make your glass measurement tight . You will need to have room to put the little glass clips that have points on them that stick into the wood sash . These hold the glass to the wood frame . Then you reapply the window glazing that you ' ve purchased . All these can be purchased at a lumberhardware store if they also offer glass cutting . Edit here ' s a decent link on glazing # 2 forgive me if I am jumping the gun . For some reason when I saw single pane I assumed that it was an older wooden window . And that the picture you provided was just to show the style . If it is a vinyl window then the same theory applies as in removing all any glass and then either using a double sided tape or simply clear silicone and then you may have to use some masking tape to hold the glass in place while it dries . Approximately 12 days