When completing 2018 income taxes for my mother who died in 2019, what do I do about the signature line? And do I fill out the date of death or leave it for next year?

I am looking to complete the 2018 income taxes for my mother who died in Feb 2019.  She did not have a will but as her adult child I am completing this.  I am just wondering if I am to enter the date she died on page one or save it for next year?  Also, what do I do about the signature line.  Do I sign it or should I leave it blank?