Hello Emma,
even in LV5.1 you should find a function called "Sum up Array elements", probably in the math palette.
If you want to do some special math, you can use a simple For-loop and sum up the elements by yourself.
Best regards,
GerdW
Best regards,
GerdW
using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019