Because that is a very old and no longer supported version of Jomsocial you would need to follow a list of instructions to get your version up to the latest one. You only need to purchase a subscription and this gives you access to the versions all the way up to the latest one.
As i don't know your joomla version if you are using joomla 1.5 then you would also need to upgrade that as well if this is the case then it can get very complex depending on what is on your site and your skill level.
Please note that we can assist with advice and provide help files for you to upgrade but we are not able to do the upgrade for you