With a non-neutral barrel, you typically don't use the oak chips, which come with the kit, or at least not in the beginning. However, once the wine has gone through the barrel, if it still needs oak or if another flavor (layer) of oak is needed, the chips can be used while the wine is still in the barrel or anytime afterward.
A barrel is considered neutral when wine, which is left in it for a considerable amount of time, has not received any oakiness from that barrel. That amount of time is pretty subjective, but for me, if no oakiness has been applied to the wine while in the barrel for 4 to 6 months, I would consider the barrel neutral. (Others may have a different opinion.)
Once the barrel is considered by you to be neutral, you can use the barrel for just micro-oxygenation (my favorite reason for having an oak barrel!) and add oak chips, staves, dust, ..etc. right in the barrel, just as you would in a carboy.
Hope this helps.