How do I claim and receive full credit for my 80 year old mother in law living with us and my wife and I providing housing, food, rides, care etc

If she had taxable income less than $4,700 and you provided more than half of her support you can claim her as a dependent. 

To claim your mother-in-law as a dependent, you only need Form 1040 which is included in the Free version.   You can see which forms are available in each product by clicking this link and scrolling down.    You can always start in the Free version and if something comes up while you are preparing the return that requires Deluxe or Premium, you can upgrade then.  

How to Add a Dependent

Not sure what you expect "full credit" to be.  When you claim an adult dependent you get a $500 credit for other dependents that can be used to reduce your tax liability.  It is non refundable.  

CREDIT FOR OTHER DEPENDENTS

https://ttlc.intuit.com/questions/4499708-what-is-the-500-credit-for-other-dependents-family-tax-credit

Her social security income is not included in the $4,700 income requirement for a dependent if it is not taxable, buy you still need to supply over half of her support for her to be a dependent. You can use this IRS tool to determine if she qualifies:

Test to determine dependent status