Its pretty simple, search php.ini for the following lines.
PHP Code:
upload_max_filesize = 10M ;
post_max_size = 20M ;
The above would be an example of changing it to 10mb.
Please note I believe sometimes you need to also consider the following:
PHP Code:
memory_limit = 8M ;
If you still have issues after trying what ive suggested editing, you might want to try changing the above line to a larger value. It basically is the memory limit for php files on your server and sometimes can prevent uploads from working.
Dont forget you may need to restart apache for the changes to take effect.
Now if this fails, providing you have an apache server and apache uses PHP as a module, you can also make changes to the .htaccess file usually in the root, adding a few simple lines.
Something like this:
Code:
php_flag file_uploads On
php_value memory_limit 8M
php_value post_max_size 20M
php_value upload_max_filesize 10M
Hope it helps
Matt