calc YTM on calculator

On candidate resources fixed income number 1 question 2 im able to get all the spot rates but then they say calculate the YTM for the bond using ur calculator. what inputs do I use. the spot rates are .055 yr 1 .0625 yr 2 .07 yr 3 and .0825 yr 4…its 4 % coupon treasury bond maturing in 4 years…they get a YTM of 8.14 % i just dont know how to do it…can someone please help?

thanks