Setting the number of periods per year
Usually the calculator is set at the factory for 12 periods per year. We want it to be set to 1 P_Yr. You can verify this by pressing the green (or orange) second function key and then holding down the CLEAR ALL key (above the INPUT key). It probably shows 12 P_Yr. If it does already display 1 P_Yr, you can skip this section. If you do need to set the calculator to 1 P_Yr, press the 1 key and then press the green (orange) second function key and then press the P/YR key (above the PMT key in the top row). Now verify that you have set it to 1 period per year by again pressing the green (orange) second function key and holding down the CLEAR ALL key.

Changing the number of decimal places displayed
Your calculator always keeps all calculations internally to 9 decimal places. You can control the number of places it displays simply by pressing the green (orange) second function key, then the DISP key (above the = sign) and then an integer from 0 to 9. Remember, the result of a calculation is still always kept internally to 9 places regardless of how many places you choose to display.

My answer is always slightly off
There are two common reasons why you keep getting the wrong answer (besides the obvious one). If your calculator is displaying the indicator "BEGIN", you need to press the green (orange) second function key and then the BEG/END key (above the 0) to toggle off the "BEGIN" indicator. "BEGIN" refers to what are called "annuities due" in which the payments are at the beginning of each of the periods, and we normally want to solve "ordinary annuities" in which the payments are at the end of each of the periods. There is no "END" indicator. The absence of an indicator means the calculator is set for ordinary annuities which is almost always what we want.

The other common reason for not getting the correct answer is failing to clear the calculator's memory registers before beginning a new calculation. It is not enough to simply press the "C" key in the lower left corner. This clears only the current display and not the memory registers. Before beginning each new calculation, get in the habit of always pressing the green (orange) second function key followed by the CLEAR ALL key (above the INPUT key).