If you see an error like “The uploaded file exceeds the upload size” when adding a theme or plugin, you just need to raise a couple of PHP limits for your site.
Use cPanel (no files to upload)
Log in to cPanel.
Go to Software → MultiPHP INI Editor.
Select your domain and set:
upload_max_filesize:
64M(or the smallest value that fits your file)post_max_size:
64M(must be ≥upload_max_filesize). This can be larger than upload_max_filesize if required, but must at least be equal to upload_max_filesize.
Click Save.
Tip: Don’t set these excessively high. Very large values can waste resources or be abused.