How to change image upload folder permission?

You need to change the permissions of wp-images to 755 or 766 or 777. It will differ according to your host.
That okay ?

Should I change this 755 permission in a .php file in the root on my WP blog’s server? On the below listed page they say to change it to 666, so not everyone can get in, but it’s not even clear to me if I need to change that on my FTP or in my WP admin panel?
https://codex.www.ads-software.com/Changing_File_Permissions

I really am a newbie, I have no clue how to change that, I’m trying to select the wp-images folder, but it just gives me a text file with my username before each file.

It’s the folder you need to change, not a file.

A file can be 666
A folder should be – in this case – what I wrote above.

What ftp client do you have ?
https://www.tamba2.org.uk/wordpress/ftp/

You can also do it Using Internet Explorer

log to your site using : ftp://yoursite

click on file –> LOG In As

then right click on the folder you want to change permission

Then go to Propreties —> Permissions .

Et Voila !

Hope this can help you .

You guys are awesome, thanks so much for taking the time to help out ??

I got it to work by using Hostgators File Manager in the cpanel. They even have a nice movie on how to do what you told me earlier:
https://www.hostgator.com/tutorials/xskincpanel/cpanel_xskin2_filemanager.htm