For a stay of three months, will not need visa.
If you want to stay longer, you can extend your visa, but you must go with your passport to the headquarters of the federal police in the city where you are, fill one or two papers, and pay a small fee.
Eventually, photos of identity, proof of solvency, and your return ticket will be required.
Bring your notebook international health, ensuring that you are well vaccinated against yellow fever, which is mandatory for visiting certain regions of Brazil, and also to cross the border from certain neighbouring countries. An insurance to cover your medical expenses (reimbursement of the cost of medicines and consultation or hospitalization, medical repatriation, etc…) can be useful.
The yellow fever vaccine is strongly advised if travel is planned in Pond Amazon, in certain areas of the Northeast, and Pantanal.
Vaccinations against hepatitis A and B are also recommended, as well as tetanus, polio, diphtheria and typhoid.
Finally, consider asking your doctor treatment against malaria, especially if you travel Pond Amazon.