Unfortunately as they say "there's no such thing as a free ride". It's important to understand that free proxies are never safe or secure.
Proxies by their very nature or not secure and provide no real anonymity. It is much easier than people realize to track someone using a proxy, in many cases proxies make it easier to identify someone.
Instead of using a free proxy which is not secure, you should consider the use of a VPN account. A VPN account will make your entire internet connection for all programs secure and anonymous.
If you choose to use a proxy remember, that none of them are safe or secure and that most are setup for people to use with bad intentions. For true security and anonymity you really need a VPN account.