In order to update the TriCaster software, exit out of the TriCaster software to Windows desktop. From there, open the web browser and navigate to the NewTek Updates and Downloads Page.
From here, you can either scroll down to the TriCaster (Legacy) section or type in either TriCaster 455 or TriCaster 855 at the search field at the top of the page:
Here, you will find links to various legacy TriCaster software updates. Select either the TriCaster 455 link or the TriCaster 855 link depending on which system you have.
There are 10 parts to the update. You will have to download them one at a time to the same folder and run the .exe file (which is included in the 10th download) after you have successfully downloaded all 10 parts.
Warning: Doing this step out of order will cause the update to fail.
Below is an image of the TriCaster 455 update list, for your reference: