net assignment question

hello

how can i assign a net as a ground or power?

based on the artical below, i should identify the power and ground nets in order to maximize the performance but i do not know how.

https://community.cadence.com/cadence_blogs_8/b/pkg/posts/how-to-maximize-performance-when-your-package-layout-gets-complicated

i assume i need to assign some nets as ground or power in the constraint manager.

currently all nets on the netlist are assigned as a signal net so any command takes a long time to execute.