Change domainname of shop

[Novios]

I hope someone can help me with the following. I use multistore and now I want to change the main-domainname of one store. I could easily change it in Prestashop of course, and the shop works now on the new name. The old name is also there, but not as the main url of the store.

 

Now I want to change this for Google as wel, I believe 301-redirects are necessary? How do I do this?

When I want to change the address in Webmaster Tools I get the error that there are no 301-

Want als ik in webmaster tools de adreswijziging wil doorgeven geeft hij aan geen 301-diversion guidelines are found for the website?