Hi,
You no need to get data from function module.
Just make your text as include text as shown in screen shot of madhu and sushmita and pass the text name, text object, text ID and language(For all these attributes goto QA32 were your long text is maintained and double click on containeer than in menu Goto->Header ).
Than automatically the text from QA32 long text will display in your text.
And about SO10 it is used to maintain dynamic text here you no need to think about it because your text is coming from QA32 long text.