Updating older macbook pro

I have an older Macbook Pro (from 2009!).

Originally purchased to record music with an Apogee ensemble interface.

Both are rather dated, but I can use the Ensemble as a standalone unit (for mic preamps) if I update the firmware through Apogee.

To do this, I first need to update my Mac OS from 10.5.8 to 10.7.

Apple Support by phone could not help me.

Does anyone have an idea on the best way to do this ?

(It may involve the apple website, but unfortunately my macbook won't connect to internet ('Cannot establish secure connection')). I think it may be related to the older OS...