Go to the website of the Brazilian consulate. There you will find a list of documents and fees that you will need to submit. as far as invitation letter if you show proof of ample finances, bank statement. also if you are staying in a hotel and have a copy of your reservation.
A letter of invitation (original or clear copy) written in Portuguese from the sponsor in Brazil is required. It should be addressed to the Brazilian Consulate General, typed on letterhead, signed, and should contain the following:
Relationship to the applicant and purpose of travel
Dates of travel and place of stay
Contact information in Brazil