Refurbished computer

Once again, to deal with MS stopping support of a particular version, I've purchased a new (to me) refurbished computer. Probably not what MS would prefer, but they work fine for a low cost and provides what I need (and it will work just fine until MS stops support on "11").  Everything seems to be working fine, but I have been stymied by my inability to add a sign in pin.  The 'puter just boots up without asking for a password or pin (as "admin").  It is an in home only computer so I am mostly not worried about anyone else using it, and I never keep sensitive information on it, but should someone break in and steal it they would not even have the most basic of hurdles to jump over.  How do I add a pin or password to reopen my computer.  IN settings it says Pin is not available.  I do not want to use my MS password every time I want to open the computer.  It is long and complicated.  I am also concerned about what to do if I accidently put it to sleep or lock it.  I have no way to wake it up or unlock it.  I assumed that when I first booted it up there would be an opportunity to add the pin.  did not happen.  

Ideas?  Thanks in advance.