Hi,
fields inside a repeating section cannot be connected to SharePoint columns because there is no matching between one column and N fields (one for each repeated section)..if you need, you can connect the whole repeating section to a multiple lines of text column and there you'll find the xml content of the repeating section..
In case you need data from the repeating section inside a workflow, you can query that field otherwise you can query the hidden item property "Form Data" where you'll find a node corrisponding to the repeating section and inside it an encoded xml version of its content..
Giacomo
Here is a video that walks through how to set up the repeating section and form controls to connect to the list appropriately.