The Baby Bjorn One is designed for front and back carries.
The instructions are here.
There are more videos listed on the Sling Surgery main website.
The Sheffield Sling Surgery website is here - full of useful information about safety, all sorts of articles about warm/cold weather carrying. knee to knee support, big kid carrying and so on (direct link here) and a post about how to choose a sling here
The library drop in dates link is here and you can also book some personal help here.
Facebook page is here and the online support group the Virtual Sling Surgery is here