Thank you. The WPS button -- if it exists, and it may not -- is on the wireless access point, not on the printer.
WPS is a relatively recent addition to the wireless world, and the majority of wireless access points do not support WPS. Only the newest routers support WPS. For those systems without WPS, the manual method of wireless setup is required.
I'm referring to the wireless setup manual for the MX432 available at the following link:
See page 4 of the manual, excerpted below, for routers that do have a WPS button:
For routers that do not support WPS (the majority of routers), wireless setup must be done using the manual method. You will need the wireless network broadcast name, the network encryption method (usually WEP, WPA, or WPA/WPA2), and the encryption key. This information can be obtained by logging into your wireless router and checking the router's wireless setup page.
Instruction manuals (there are several) for the MX430 series can be obtained from Canon's web site at the following link:
If your router does not support WPS, I recommend using the IJ wireless network tool to connect the printer. Instructions for the IJ wireless network tool can be obtained from the Canon web site at the following link. Select "Guide for Canon IJ Network Tool (Windows)" as the option.
One final note. The manual for the MX430 indicates that the printer supports only 802.11b and 802.11g networking, not the newer 802.11n. If your router supports only 802.11n, it may not be possible to connect to the printer. In that case, it would be necessary to replace the router with a version that is b/g/n/ compatible.