that rack doesn't have the standard mounting plate for a permanent rear light. You could use something like these to make a mounting point. the first one replaces the nutted end of the quick release, or you can bolt it to something. I use this one on several bikes.

https://a.co/d/5cdVFOl

I haven't used this one, but have seen it. you can bolt it on

https://a.co/d/aI8VXLl

your rear light might not be in the right orientation anymore (most removable brackets rear lights assume a vertical, not horizontal mounting position) which usually wouldn't matter. but if you want one with an accelerometer that gets brighter when you stop, it might.

but quite honestly, if you paid nearly 40 for the rack then another 15 or so for this, I would return the rack and buy one with standard mounting points. the rack does not look especially high quality.