see morewhat hosting package do you have? are you on dedicated? vps? shared? there are a few things to do, as mentioned by LyubovL, you can edit the php.ini file and insert a line such as this:
upload_max_filesize=20mb
or you can, if hosted on dedicated server, change the php.ini from configuration of your server. just change the max_upload_filesize to whatever parameter you desire. you can also request your host to increase your max_upload_filesize limit.