Congratulations on getting a shiny, new B1. It is a great machine for beginners and experienced users alike but like all machines you will need to do some things just right to get the most out of it. This is a brief guide which explains how to put together your B1 to ensure that the mechanics will just work.
When installing the uprights it is crucial that they be at 90 degrees to the base and not the bed. The bed will be sorted out later. If you fail to ensure this then you are likely to experience later issues with ABL and/or the nozzle scraping across the print.
In order to ensure that both uprights are at 90 degrees you will need to use a set square. Eyeballing it alone is not enough and relying on the provided brackets is also not enough since they include some play by design in order to allow you to manipulate the frame to overcome manufacturing tolerances. Place the set square up against the frame and the base as can be seen in the image