is the spoiler designed for the car? is it honda oem item?

some spoilers might use different sized bolts 2 bigger front ones and the rear ones a bit smaller.

check that the spoiler has a threaded hoe for the bot and take it to bunnings warehouse and find 4 bolts that screw in, without binding. does the boot of the car have a threaded hole too?
i would imagine it has a regular hoe, so it should just fit

also when at bunnnings and u grab 4 bolts from a box good chance they arent a the same bolt, because pp take them out and put them back in the wrong place