Retirement tax questions

I am receiving a death benefits from my mother's passing. The packet I received from the company does not have any info about how much or anything. It will not automatically take out taxes. My options are no taxes, a percentage, or a specific dollar amount. I do know that close to $15,000 is from interest. I do not know if the money put into the annuity was taxed or not, it was rolled over from when my mother received it from my grandmother. I am wanting to have taxes paid on it when it is withdrawn so there is not a huge impact at tax time.