In Feb '16 I invested $11K (nondeductible) into a Trad IRA ($5.5 for '15 and $5.5 for '16) a few days later is was sold and rolled over to a ROTH IRA. How do I report?

In Feb 2016 I invested $11K (nondeductible, $5.5K for 2015 and $5.5K for 2016) in to a traditional IRA and converted (rollover) it over to a ROTH IRA a few days later.  My questions are:

1.) On my 2015 taxes I thought it was a straight ROTH Purchase and that is how I declare it. I assume I need to amend my 2015 taxes to show the conversion or show it as a purchase of a nondeductible Traditional IRA?

2.) The $5.5K for 2015 that was purchased in Feb 2016.  Which tax year does the conversion go against (Trad to ROTH)?