First of all, I would like to point out that I am very new to OpenCart (as in have literally never installed it anywhere else before).
I am using the Plesk control panel, and am having issues. I am trying to install OpenCart 220.127.116.11. I have followed the instructions in the install.txt file, but am receiving an Error 500. I am not sure where to find error log files, so as of right now am unable to provide them.
I have renamed php.ini to user.ini (as per the install.txt file in the OpenCart download). I had previously tried it with php.ini and got the Error 500 message, too. I have set up a MySQL database with a user etc. too.
A 500 error message is a general message and it's hard to say what the issue might be without more details. You can check these articles to enable detailed error messages on Plesk and setup PHP error logging: