Loading a U-Boot ARM flash image into IDA Pro

I have a U-Boot image file which was extracted from flash memory of a board with an Hi3520D ARM CPU. I would like to load this file into IDA Pro and dig out the password that is required for accessing the U-Boot shell so that I could flash a modified firmware back onto the board.

The problem is that I don’t know how to find out the values that IDA needs in the "Disassembly memory organization" window. I have used IDA before with normal x86 and ARM executables but binary files are new to me in this context so guidance would be greatly appreciated.
Here is the file if it helps: dropbox link

This is mostly a learning project so as much detail as possible would be good.