Let me talk about the specific steps. Don't use the default settings for all steps!

First, create a new sequence of 1280*720 square pixels.

Then import your avi file for editing.

When exporting, select the aspect ratio of 1280*720 for output. It is suggested to use h.264 coding (the original avi is uncompressed, and it will definitely be very large), and the code rate should be set at about 5Mbps (5Mbit per second, that is, 5/8MByte), so that the video of 1 minute is about 40M.

Upstairs says premiere output is not good. I don't think you can do it yourself.