In Salesforce we can enable the Forecasts to User. Follow the below steps to enable the setup
Step 1 : Go to Setup
Step 2 : Enter User in Quick Findbox
Step 3 : Select Users
Step 4 : Click Edit Next to User
Step 5 : Enable the Allow Forecasting Checkbox
Step 6 : Click Save
This blog is very useful to learn about how to setup Forecast to users.