1. Explain it simply
可能 means 'maybe' or 'probably' and softens a statement into a guess.
Put 可能 in front of the verb or predicate: 明天可能下雨。
You can also start the clause with 可能, but never put it after the verb or at the very end.
可能 sits before 不, so a negative guess is 可能不 + verb: 他可能不知道。
2. Show examples
他可能不知道这件事。
Tā kěnéng bù zhīdào zhè jiàn shì.
He probably doesn't know about this.
可能 before 不
明天可能下雨。
Míngtiān kěnéng xià yǔ.
It might rain tomorrow.
before the verb
你可能不认识他。
Nǐ kěnéng bù rènshi tā.
Sandhi:Nǐ kěnéng bú rènshi tā.
You probably don't know him.
softens the claim
她可能去年来的。
Tā kěnéng qùnián lái de.
She probably came last year.
guess about the past
3. Share a tip
可能 always comes before the verb or predicate. 他不知道可能 is wrong. Keep it in front, right where an adverb like 不 would go.