How do I file for a Testamentary Trust? It is registered with CRA already and this is my first year filing, am I able to do it with turbo tax?

Unfortunately, there is no version of TurboTax that can be used to prepare a T3 Trust Income Tax and Information Return. However, Intuit offers another product called Profile that does have the ability to do T3 returns. You can read more about this product here: http://profile.intuit.ca/professional-tax-software/profile-onepay.jsp

Please be aware that Profile software is available for Windows only.