If you log in to direct admin, it's on the first page. Disk Space (XXX/512 MB) and Inode (XXX)
An inode is a file, a folder, or a link to a file or folder. There's other technicalities, but for your account it's pretty much just files and folders.
Spelling doesn't matter if you make the folder yourself, just make sure it matches. The POSIX standard is "/tmp" but anything inside your home folder is not subject to any real standard other than what you like. POSIX is case sensitive, unlike Windows. ~/tmp/ is different than ~/TMP/ which is different than ~/.tmp/, but really any of them is "valid". (~ is something like /home/jerome1g/ AKA your home folder). Finally, Windows uses backslashes ("\") and sometimes understands forward slashes ("/") but POSIX only understands forward slashes ("/"). So it has to be something like ~/tmp and not C:\tmp. Spaces are annoying. Don't use spaces.
Now, the kicker is when you use dirname(__FILE__), you're saying the temp folder is in a subfolder of your wordpress configuration file. If your temp folder is in the folder above that, then you need to use the "folder above this one" syntax, which is ".."
So if your site is installed here:
/home/jerome1g/domains/something.x10.mx/public_html/wp-config.php
And your temp path is here:
/home/jerome1g/tmp
We have to go up 3 folders (from public_html into something.x10.mx and then up into domains and then up into jerome1g) and then into tmp so:
define('WP_TEMP_DIR', dirname(__FILE__) . '/../../../tmp/');
or, create your temp folder here:
/home/jerome1g/domains/something.x10.mx/public_html/wp_content/temp
And use the example in my link:
define('WP_TEMP_DIR', dirname(__FILE__) . '/wp-content/temp/');
Finally, make sure your permissions 0755. 0700 is fine too, if you want to tighten security, but I'm not 100% sure that won't cause issues in some niche circumstance.
Sorry this post is so long. It ended up being a lot of explanation for "create a temp directory and tell Wordpress about it"