Q: How do I sync my Apple Iphone 6 with my computer

Caution - this sounds like something you should do very carefully.

You mention two different people - your husband (iPhone owner) and you (computer owner).  You should strive very hard to keep his information separate from yours.  You should each have different Apple IDs, etc.  You can use Family Sharing for any material you wish to share.

So, with that said, you can create a username/password on your computer for your husband's iPhone to use.  This username would only be used to house his information.  You would then be certain your computer has the latest version of iTunes (12.4.1 currently).  Open iTunes, and use the menu to go to iTunes (Mac) or Edit (Windows) > Preferences > Devices and check "Prevent iPods, iPhones and iPads from syncing automatically."  Then simply plug his iPhone into the computer using the USB cable once the computer is logged on to his account.  Choose "Back up now".

Sync your iPhone, iPad, or iPod touch with iTunes on your computer using USB - Apple Support