Hi Jade,
The best free online book with step by step examples is Forecasting: Principles and Practice by Rob Hyndman and George Athanasopoulos
https://www.otexts.org/book/fpp
They used R in the book to illustrate the examples to users. We have converted the R data to SAS dataset as well as the equivalent SAS codes for users just like you to learn forecasting using SAS. 😆 You can get the SAS dataset and SAS code from the following github:
https://github.com/alexchienTW/SAS-Viya-Forecast-Cookbook
The github contains SAS codes for both SAS 9.4 and SAS Viya.
Have fun with it.
Alex