How to add photos to my iPod nano 6 generation ?

Did you not read the manual I provided?

Check the section on syncing your iPod and while it is connected to your computer you will need to set up your photo sync preferences in iTunes.

Select the iPod in iTunes. There is a row of "tabs" (starting with Summary). Click on Photos there (a bit to the right of Summary). This is the Photos tab, where you tell iTunes how to sync photos to the iPod.

You can set it up to sync photos from a folder, a set of folders, or from iPhoto (if you use a Mac).

If you check the box for Include full-resolution photos, iTunes will put a copy of the original photo files on the iPod, which you can later access with disk use enabled on the iPod. The iPod does not use these files to display the photos on the iPod screen; they are there just as a backup copy.