Press `STAT`
Select `1:Edit`
Enter the x-values in `L1`
Enter the y-values in `L2`
Press `2nd` then `0` to open `CATALOG`
Press `ALPHA` then `S` to jump to `SortA(` if needed, or scroll to `DiagnosticOn`
Select `DiagnosticOn`
Press `ENTER` twice
Press `STAT`
Move to `CALC`
Select `4:LinReg(ax+b)`
Type `L1 , L2` after the command if not already there
Press `ENTER`
Read the correlation coefficient as `r`
Read the coefficient of determination as `r^2`