The best way would be using PI System Management Tools (PI SMT) -> Points -> Performance Equations.
Any other tool that shows the point attributes will work too but PI SMT is the easiest one to achieve this. The actual equation is stored in the extended descriptor, while the scheduling is coded in the location parameters.
I would like to invite you to take a look at the the online training PI System Manager I: Essential Skills that we provide as part of OSIsoft vCampus.
If you go to the link to the Sys Mgr I CBT Andreas included above, and on the first page choose "Site Search Page" you will find (with Ctrl-F) many references to performance equations are in chapter 10. PI-SMT is covered in Ch. 2 if you are unfamiliar with how to launch it.