In case that someone have the same question, in order to upgrade to PL2.08 via web interface of the switch, from Maintenance > Update Manager > Update Method 'HTTP' > Browse for file 'PL.2.08.gz' (YES just leave it exactly like you downloaded from the hpe site) > Update type 'code' > Image (in my case is the active image) and then press download.
Voila you just updated to 2.08
