If you install iTunes from the iTunes Download page, you can manually check for updates to iTunes, or set iTunes to check for new versions automatically every week.
See Also
How can I find which version of iTunes I …Choose the 64-bit or 32-bit version of OfficeiTunes 12 for Windows - Technical Specifications - Apple SupportWhy is Apple Dropping 32-bit App Support and How Will it Impact Your App?In the iTunes app 
on your PC, do one of the following:
Manually check for new versions of iTunes: Choose Help > Check for Updates.
Have iTunes automatically check for new versions every week: Choose Edit> Preferences, click Advanced, then make sure the “Check for new software updates automatically” is selected.
When automatic updating is turned on, iTunes checks for new updates weekly. It checks only after you have quit and restarted iTunes at least once during a seven-day period.
