Sold interest in inherited property creating capital gain of $41,901. Am told that there is a "once in a lifetime" exemption of $1.5 million. Where can I find information and/or IRS forms on this exemption and how do I take that exemption this year?

Sorry - there is no "once in a lifetime" capital gain exclusion. There is an exclusion available if you sell your principal residence, and there are lifetime gift and estate tax exclusions that reduce the amount of gift or estate taxes you (or your estate) might have to pay, but neither of those apply here. Assuming that the property was not your principal residence, if its value appreciated $41,901 from the time you inherited it (based on the fair market value as of the decedant's date of death) to the time you sold it you report the gain on Schedule D.