Here's info regarding how to create and edit an php.ini file.
1. Enter your cPanel account and press on "File Manager"
2. Click "Go".
3. Go to folder you that contains your scripts or stay in the public_html folder if you want to apply rules for all scripts, not specific ones. Click on "New File" and enter "php.ini" as a filename.
4. After the file is created (or if it already existed) choose it in file list and click on "Edit" or you may right click it and click "Edit".
5. Simply hit edit to agree.
6. Enter your rules that you need and press "Save Changes".
If you want your php.ini file to work for all scripts in all sub-folders, please check this thread:
Load php.ini recursively for all subfolders