To Be Attached
intransitive verb, godan verb
You know that the word 付ける means "to attach" and you know that the kanji 付 means attach. So, this word probably has something to do with attaching. This is the intransitive version, though, where something is attached (and you're not doing the attaching). You can use the く as a hint. You see something attached on the wall. You say "Coo'"
The reading can be derived from 付ける, a word you should have seen a few levels ago. If you know that word's reading you should be able to figure out this word's reading as well (and vice versa).
この手紙には、まだ切手が付いてないですよ。
There's no stamp attached to this letter yet.
あーあ。白いティシャツにケチャップが付いちゃった。
Ugh, some ketchup got on my white tee shirt.
あなたの耳たぶに付いてるそれ、何？
What’s that thing attached to your earlobe?