Fatal error: Allowed memory size of bytes exhausted – NEED DUMBED DOWN

I have been getting this error when trying to upload an image..

Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 41296 bytes) in /home/nschwall/nschwaller.com/wp-includes/media.php on line 253

and I’ve got the advice about doing the following

1. Try adding this line to your wp-config.php file:
define(‘WP_MEMORY_LIMIT’, ’64M’);

2. If you have access to your PHP.ini file, change the line in PHP.ini
If your line shows 32M try 64M:
memory_limit = 64M ; Maximum amount of memory a script may consume (64MB)

3. If you don’t have access to PHP.ini try adding this to an .htaccess file:
php_value memory_limit 64M

4. Talk to your host.

but I need someone to dumb it down for me if possible. How do I get to my wp-config.php file or my PHP.ini file or whatever I need to access and change?

Dreamhost is my server and I am running version 3.0.3 with the theme twenty-ten 1.1 for what it is worth.

THANKS!