¿como actualizo mi ipod touch 8 gb a ios 5?

I suspect you have a 2G iPod. Those can only go to iOS 4.2.1.

Identifying iPod models

iPod touch (3rd generation)

iPod touch (3rd generation) features a 3.5-inch (diagonal) widescreen multi-touch display and 32 GB or 64 GB flash drive. You can browse the web with Safari and watch YouTube videos with Wi-Fi. You can also search, preview, and buy songs from the iTunes Wi-Fi Music Store on iPod touch.

The iPod touch (3rd generation) can be distinguished from iPod touch (2nd generation) by looking at the back of the device. In the text below the engraving, look for the model number. iPod touch (2nd generation) is model A1288, and iPod touch (3rd generation) is model A1318.

Google translate

then on the back I get Actualize MI model A1367 ITUNES NOW BUT NOT LIKE TO BE ABLE TO DOWNLOAD IPOD applications like FACEBOOK

Your only way is if you have your previusly purchased the version that was compatible and that version is on your computer such as in the recycle bin/trash or in a computer file backup. In that case delete the current version that is in your iTunes App library and replace it with the older version. Then sync.

Also see:

Recover Older Versions of iPhone Apps After Updating — Apple News, Tips and Reviews