User manuals for most Verizon phones are available from the Verizon support page located at verizonwireless.com/support. Once there, select the specific model of phone with which you need help, followed by clicking the View Your User Guide option.
You can also visit the website of the manufacturer of your phone and search the support for that particular model. Numerous types of cellphone manuals are available to download in PDF form or for view directly in your browser.
There are also websites that specialize in cellphone manuals, such as Manuals Online. Some of these sites feature manuals for older phones that may no longer be supported by Verizon.