start up script ?

I need to run a script every hour on my asus rt-n66u, this one:

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cru a IPUpdate "*/60 * * * * root wget http://www.unotelly.com/unodns/auto_auth/hash_update/updateip.php?user_hash=your_token"


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Under tools, I can send this as a command. But how and where do I enter this script so the router will do this every hour (without me entering it manually)?

I dont know much about that scripting, please explain with simple words :-)