I'll try and explain but I'm not great at this!
www.familysearch.orgBrowse by location - click on British Isles
Historical Record Collections - this gives a list of all collections - some say "Browse images" - just click on appropriate collection.
Others such as England, Lancashire, Cheshire, Yorkshire do not say browse images but if you click on this collection then scroll down the page to "View Images in this Collection" the next line says "Browse through 332,814 images" - click on this and it will give a list of Lancashire, Cheshire, Yorkshire. Click on appropriate county and up will come a list of the parishes - click on parish and it will give baptism, marriage or burial and dates covered. Not all parishes and not all years are covered but there are quite a few.
From the years covered e.g. 1887 - 1897 it will give no of images - this is where an educated guess comes in - divide the no of years by no of images and put in e.g. Image 150 - press enter and up will come a page of register with date - if too early try later and vice versa.
Can be long winded but practice helps and loads of free marriage certs with original signatures.
Good luck!
