There are two way to get to Manu:
It is also possible to use the combination of travelling one way by bus/boat and the other by plane.
It is important to get permits in advanced to enter to the park. INRENA http://www.inrena.gob.pe is the Government office in charge of issuing permits. This can be done and paid for through the 8 different official operators in the Manu park.
There are several lodges and camps in the Manu area[http://www.peru.info/e_ftociudadeseng.asp?pdr=660&jrq=3.16&ic=2&ids=1309].
Manu Wildlife Center is an awesome place to see lots of birds, monkeys and other wildlife. Cabins are clean, with hot water, but no electricity. Food is very good. Various trips are available from canopy stands to one of only a few known Macaws clay licks, where hundreds of Macaws come every morning to eat bits of clay which aids their digestion.
Contact an official tour operator in the area. Promperu official tourism site[http://www.peru.info/e_ftonaturalezaeng.asp?pdr=920&jrq=7.1.1.3&ic=2&ids=1829].