This is a guide to replacing files because I warned Arisaka about this. So, I'm setting up a guide for that. Here are the steps:
First, look for the file to replace.
It will lead you to this.
This is a "photo profile." Scroll down your window.
As you can see there a little link in the rectangle. Click on it.
It will then lead you to this.
Click on the button in the rectangle. Then select your file you will use to replace the lower quality one.
Change the file's name only when required.
This where you type what's changed in the profile. Most users don't commonly use this; this is optional.
Then click on the button in the tiny rectangle.
Then you're all done!
If you have any questions or concerns about this, direct it to the comments section or contact me on my talkpage. Thanks! :D