It depends if you want to say it as an experience or if you have been doing many times. For experience you can say "Eu (já) viajei ao Brasil." or "Eu tenho viajado ao Brasil." if it happened many times.

Both "Eu viajei" and "Eu tenho viajado" are correct to say. However when we say "Eu tenho viajado" it may sound like a very formal language or a frequent experience I guess. So much so that you can add how many times you have traveled to Brazil, like " Eu tenho viajado ao Brasil duas vezes" or "Eu já viajei ao Brasil duas vezes" (I have traveled to Brazil twice).

In Portuguese say "I have Traveled" (Eu tenho viajado) the impression is that you are still traveling, the action is still happening. The correct is to say "I traveled to Brazil in the last" (Eu viajei para o Brasil no passado). or could also say "I Have Been Traveled"(Eu tenho viajado), which means you still travels ... I hope have helped you!

If you went to Brazil once or a few times and it's been a while, say: “Eu já fui ao Brasil” or “Eu já viajei para o Brasil.” If you usually go to Brazil, say: “Eu viajo para o Brasil sempre” ou “Eu costumo viajar para o Brasil (nas minhas férias or a trabalho or uma vez ao ano...)

You can simply say "(eu) já fui ao Brasil", to state that you have ever been in Brazil.