Treat it as any other table source: SELECT * FROM dbo.MyFunction(param, param)
Having said that, the rCTE string splitter is known to perform poorly against other methods. You can read about it in this article [/url]which offers a much faster alternative.
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden