Create php.ini under your home directory and past the following value.
upload_max_filesize = 10M
post_max_size = 20M
OR you also can set this value in .htaccess, if you are using .htaccess then you can use the following.
php_value upload_max_filesize 10M
php_value post_max_size 20M
If still you face the same problem then you should add the following line in your wp-config.php
define(‘WP_MEMORY_LIMIT’, ’64M’);