Basically... it IS complicated! I never use it.
Some of the functionality comes from the settings buttons in the top right corners of columns. They let you pin columns open permanently, so you can extend the interface sideways. This is suited to wide monitors on desktop computers.
You also need to use the icons in the top left corner a lot more as the labelled links are hidden easily.
I just use the normal mode ? But a lot of people swear by the multicolumn mode so this is for them!