I just got a GoPro camera myself. The free editor software that you can download from GoPro is really pretty good and designed to work with those clips. You can export from it into one of the formats that will work in Camtasia if you want to take the GoPro clips farther.
This is something you should be aware of going forward. The Camtasia Studio editor can only work with 30fps footage. What does this mean?
The clip bin can import higher frame rate footage. However, when you place it on the timeline. The editor will discard frames until the footage retains 30fps or less.
Plus, it cannot handle 4k footage. Camtasia is limited to a maximum timeline resolution of 2048 x 2048. If you import 4k footage it will be down-sampled to 2048 x 1152. That will have an adverse effect on video quality.