To increase the brightness of your clip:
Open your clip in the editor by clicking the edit button.
Click any segment on the timeline that you want to adjust.
When you select a segment, a video panel will open on the right side of the editor.
Below the filter presets in the style settings, you’ll find a brightness slider.
Use the slider to increase or decrease the brightness for that segment.
If you want to adjust the brightness for the entire clip, repeat this process for each segment by clicking them one by one and adjusting the slider.
Preview your clip to ensure the brightness levels are as you want.
When satisfied, click export.
For a step-by-step visual guide, see the attached video.