Login to your asterisk pbx as admin to create inbound route.
Inbound route is where you add your DID number ( phone number ), and route calls according to your requirement.
You can set your calls to go to IVR welcome greeting, Ring group, any particular extension or voicemail.
Create Inbound Route
Go to connection and click on Inbound route, add your DID number you have purchased phone number from your VoIP provider.
Select it destination where you want call to send.
Take reference from this screenshot.
In net topic we will learn how to create IVR