On the bulletin board in the Tower you can flag this side-quest. You need to find lavender herbs to make incense with. The locations for these are marked on the map.
You can double up this one with the dulse side-quest very easily since they are not really all that far apart - and it gets you two for the effort of one!
Simply head to the markers on the map and search around for some. Actually I remember lavender from our garden when I was a kid and to be honest? It was very visible as far as plants go - so they make finding it a bit on the hard side here.
Anyway you need to find six (x6) Lavender which should not be a problem among the three or so patches that are on the map.
Return to the marker at the Tower to turn in the flowers and collect your reward - and hey you helped make the place smell nicer! The other survivors will LOVE you for that!