Pictory allows the capability to choose a video resolution as well as change the aspect ratio of your video.
To find these options, navigate to the Format tab on the left side of your screen.
At the top, you can choose either 720p or 1080p video resolution, whichever is better suited for you. Please note that using 1080p for your video resolution will entail a slightly longer generation time.
Below, you can choose to change the aspect ratio of your video if you do not like how it looks currently.
Please note that changing aspect ratios can drastically change your video's look and can have undesired consequences. To avoid any issues, you may consider deciding and finalizing your aspect ratio before beginning adjusting any other options.