There is no magic fix for this. That's why it drives TV stations crazy when people provide upright phone video of events for a news report.

You can enlarge the video to 178% its size. That way it will fit width wise (and you'll lose some of the top and bottom). Nearly doubling a video's size, however, can also make for a blurrier, less-clear picture. But that's the compromise you have to make with badly shot video.

You can also use this trick, which is what they usually do when they use phone footage in TV news reports. The tutorial is for a different video editing program but the principle is the same.