You can use navigation drawer to do basic navigation.
You can open the drawer by touching the button, located at the left upper corner or by swiping from the left edge of the screen to the right.
Currently opened book is displayed by default. Touch this to see more options.
On expansion, you can see different options for book selection.
You can go to section "Bibles" to change your primary bible version for reading.
To change version of "Secondary Bible", read HERE.
For those who like typing, you can type a verse references or multiple references in search field and select the verse to open the whole chapter.
Read HERE more for search features.