Recorded notes and controller data always go into the currently record-enabled section (as well as the current take for the record-enabled player). To record-enable a section, either choose it from the pop-up menu in the Ensemble window, or click any instance of it in the layout grid of the Arrangement window. A red bar appears on the currently record-enabled section in the Arrangement grid.
When using sections in FreeStyle, you can think in terms of “patterns”, but you don’t have to. You can handle sections in a linear fashion as well. FreeStyle even lets you go back and forth between thinking linearly and thinking in terms of patterns.