treat it similar to English lavender. remove spent blooms and if it needs pruning do it lightly after flowering. Do not cut into old wood as it rarely sprouts new growth. I also know it as French lavender. L stoechas.
this is the RHS advice.
https://www.rhs.org.uk/plants/popular/lavender/growing-guide

OK Thanks Eileen. Will it bloom again this season? Should I give it a feeding? I have Doctor Earth Organic Fertilizer and Alaska Fish Emulsion fertilizer. Would any of these be good for the Lavender? It has the most amazing fragrance and I clipped a bundle for the house. It freshens up the whole 1st floor. Thanks again.

you may get more flowers in a month or so.
as for feeding they are happier in low nutrient soil. the link should say none needed if I remember what I read.

Paul, I have this on my rockery, we call it French lavender as Eileen mentioned previously. I trimmed all the spent flowers and there are new ones emerging.
I snipped the faded blooms as they were finished, one by one. My leaves look ok. I watered the lavender in pretty well in the first weeks and it’s pretty much doing fine now.
It’s on the top of the sloped rockery, in full sun.

Ok so it's French Lavender. That's good to know. I might have watered it too much at first. That could explain the yellowing leaves. I hope it recovers but I can't stop the rain. We get horrendous thunderstorms that flood everything, but I'm atop a hill so it drains quickly. I will check out the site.

Kate: I'm glad to hear yours is doing well. After I got mine home, I checked the label and it was the same one you mentioned in your previous question. They wouldn't be selling it here if wasn't suited for my climate so we shall see. I'm really loving it - would hate to lose it. Thank you both.