I struggle through it the first time also, but manage to get it to work. The instruction was good but like you said, it was too vague for me also.
I don't have the camera yet so i have no idea how to get that working.
Here is what i did with window base PC.
1. download the image file here: http://docstech.net/OctoPiMirror/
I choose the latest one ( 2015-01-31-octopi-0...), this take a while (for me @ 1.1GB).
2. download the Win32 Disk Imager here: http://sourceforge.net/projects/win32diskimager/
3. Install Win32 DiskImager, put SD card that you will use for your Octopi in to PC and use the software to burn image to the blank SD card.
4. connect Octopi to the LCD screen via HDMI, usb keyboard, and mouse, and power up the Octopi with the SD card installed.
5. Unit should boot up in Config screen (Like in TOM's Guide video), expand the memory to use the full size of SD card.
6. You can setup user name/Password if you like, default is
User: pi
Password: raspberry
7. In Reboot Setup, set it to boot to desktop and then reboot the pi.
8. It will boot in GUI environment, select WIFI and setup your WIFI dongle.
9. Once it show connected tot he WIFI, disconnect the monitor and keyboard and mouse devices, connect the USB of your 3D printer and reboot.
On your PC that connect on the same network, open the browser and type in "http://octopi.local/"
The interface may need to be to auto connect, but everything here should be very intuitive.