Are you using Korg DS10 Plus on a non european DSi?
If so - Dual mode should work fine ( but don''t need to worry about that at this stage)
Load up Demo1 - click on the 'Song' button - then hit 'Play' - the whole song should play through over and over.
If you you click the 'song' button again - it should enter normal 'pattern' mode - you then just select one of the 16 patterns with your stylus and it will loop that pattern until you select another pattern or click on song mode.
best to play around with it although there are always new things to learn