If you are on a Blackberry 8100, then chances are you have Blackberry OS 4.2 unless you have upgraded your OS. HippoMobile require OS4.3 or higher.
To download an updated version of the OS and install it, you should google based on your carrier.
Example - If you are on AT&T, the Google with these keywords: handheld software AT&T
That will get you the right link to the Blackberry software download site. Then select the 8100 from the list and follow the instructions to download. You will need to have the Blackberry desktop software installed on your PC (on the CD that came with your Blackberry - but you can also download that as well).
