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.