hi, i would like to ask if how can i install skype in my powerbook G4 2005 with Mac OS x 10.5.8

hi, i would like to ask if how cani install the skype in my powerbook G4 2005 and is there anything that i need to update that i need to do. i tried many times to download skype but it said that cannot be opened because its not available in the architecture? and 2nd question, powerbook has no webcam, can i use any web camera to attached in the laptop or there is a certain webcam or product that i need to use. hope theres a positive answer.. thank you...