This is almost an exact duplicate of a question asked a couple of weeks ago.

In Premiere you will find a number of video effects you can drag abnd drop on your clip to 'effect' it any number of ways.

One of those (and I can't tell you where it is offhand because I use a differetn verions of Premier to you) will allow you to change brightness and contrast. I'm sure once you've found it, it has a really obvious name.

once added then do have a play with the settings. I typically find that adjusting brightness on its own is not the best practise, which is probably why brightness and contrast are part of the same plugin effect.

Also, remember that the correct settings for one bit of your clip may not be thebest settings for another section so be prepared to keyframe the effect where necessary.

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