I contributed more to my Keogh profit-sharing plan in 2017 than I should have. Can I apply the excess to 2018? What form do I use (and is it available in Turbotax)?

I contributed about $900 excess during 2017.  I prefer to just apply it to 2018, but if I need to refund it (to myself..I am self-employed) I will.  I'm not sure what form to fill out (if any), or how else to handle it.  Can this be done within Turbotax?