I have made an example of time series forecasting with R, demonstrating currency exchange rate forecasting with the ARIMA and STL models. The example is easy to understand and follow.
R source files are provided to run the example.
The example was produced with R Markdown. If you want to learn R Markdown, you can try the Rmd source file, which is also provided.
Check the example and source files at http://www.rdatamining.com/examples/time-series-forecasting