I installed the Website Monitoring app with any problem, but I am unable to find the new "Data Input" to setup a new Web Monitoring Input.
I am logged as Admin.
Also had the same issue, the previous answer didn't work with 6.3.x
However, use the status overview dashboard, and there'll show up:
No website monitoring inputs exist yet; create one to monitor a website. Create a website monitoring input now.
Link leads to ../en-US/manager/website_monitoring/adddata/selectsource?input_type=web_ping&modinput=1&input_mode=1
Can create an input, but have to repeat the same URL as it does not show up in the Data Inputs screen. So not a solution but workaround.