Hello @newwper3,
You can increase the file size from here by navigating through WP-content/plugins/WPUF/Post Form/ image upload field, edit the field and click on advanced options on the right. Please check out the screenshot.
There you will find the field in KB format, so if you want to limit your users’ image for 1Mb, you need to insert this number 1024. then save the form. Your users will be unable to upload image more than 1Mb file size.
Default file upload size for WordPress can be set in your php.ini file’s upload_max_size value. Usually, php.ini file will be in the directory where you have the wp-admin, wp-content and wp-includes folders of WordPress. If you edit the php.ini file, make sure you restart your local server to see the modification.
Regards,