NoMy answer: its past tense is "could".
You don't, as it's not a verb, it's a noun.
Need takes an -s in the 3rd person singular ( eg she needs) , and -ed for the past in all persons and numbers (we needed, and we have needed).
amo amamus amas amatisamat amant
Je cherche, tu cherches, il cherche, nous cherchons, vous cherchez, ils cherchent. See Related Link