Bem-vindo(a) a Angola!
* Bem-vindo means "welcome" and is used for a male person.
* Bem-vinda means "welcome" and is used for a female person.
* Bem-vindos means "welcome" and is used for multiple people.
* Bem-vindas means "welcome" and is used for multiple female people.
You can also use the phrase:
Seja bem-vindo(a) a Angola!
This translates to "Be welcome to Angola!".
Both phrases are commonly used and appropriate.