take opener out be turning the screws on your pivot hinge,then sliding the curved part of hinge out of its housing,once you have opener out take the alluminium covers from the outside of opener,then mesure glass to get made up to correct size,then put opener back in untill you have glass,then take opener back out same way and push glass out as it should be held in by a sealent,replace glass then re-fit.hope this helps
shaun www.sdwupvcrepair.co.uk, November 2008