txt entry in my DNS service

txt entry in my DNS service

hello friends, I made a contract with an email marketing service..
and I need to put a txt entry in my DNS service.

The entry is:
v=spf1 include:spf.redehost.com.br ~all 

So... where and how can I put this in DNS service ?
Sorry, I don't understand nothing about that.

Please, could you help me ?