One of the entries into Brazil when coming from Bolivia is Corumbá. It is only a few km from the Bolivian city Puerto Suarez from where you reach Corumbá by bus. The immigration office (migracao) is at the bus station. Sometimes you may need this office even when arriving by plane from Bolivia and the immigration officer at the airport is not there. This might be a problem if you are not a citizen of either Brazil or Bolivia because you may get troubles when you leave Brazil without an entry stamp in your passport. So if you arrive at Corumbá airport without seeing any traces of officers of the migracao just take the bus - if available - or a taxi to the Rodoviaria, the central bus station of Corumbá and go to the migracao there. If you find the office closed (which might happen if no buses to/from Bolivia are leaving/arriving) try your luck at the bar and ask for the responsible of the migracao. If you are lucky he is there having a drink and he will go with you to his office, open it and check your documents (from Bolivia also the Vaccination Certificate for Yellow Fever) and stamp your passport.