Basically, you need to increase the size of the following values above what you want your maximum value to be (except for uploadmaxfilesize which you can keep at exactly what you want the limit to be). Here, we want our max file size to be 10MB.
memorylimit = 32M
uploadmaxfilesize = 10M
postmax_size = 20MOf course these go in your php.ini file which is usually in something like "/etc/php5/apache2/php.ini" or equivalent/similar file path.