CMW and NANDroid backup I found a CMW .img file another user used for same model, is that the right one or are there different CMW links?

If it is the right one, or you link a CMW download, the next step is
to write 
adb reboot bootloader
fastboot flash recovery cmw.img
fastboot reboot

How do I get the Nandroid backup after that?
Thank you
clockworkmod-recovery, twrp and other image files are always specific to a device (brand+model). So if the image you found was for the very same brand and model, it should fit. But keep in mind that some manufacturers have slightly different models going by the same name (e.g. Samsung often does that), so make sure it matches. For TWRP, you can check on officially supported devices here (and also download the images from there)
The steps to install it are indeed to boot into fastboot and flash the image. But as pre-condition, the bootloader of the device must be unlocked (see: bootloader-lock tag-wiki)
with the custom recovery (CWM or TWRP) successfully installed, boot to recovery. You'll find the backup menu there – that's the nandroid backup.