1. Explain it simply
因为 introduces the cause, and 所以 introduces the effect.
The 因为 clause comes first; the 所以 clause comes second.
You can drop either 因为 or 所以, but never swap their order.
2. Show examples
因为天气不好，所以我没去商店。
Yīnwèi tiānqì bù hǎo, suǒyǐ wǒ méi qù shāngdiàn.
Because the weather was bad, I didn't go to the store.
cause to effect
因为工作太忙，所以他不能来。
Yīnwèi gōngzuò tài máng, suǒyǐ tā bù néng lái.
Because work is too busy, he can't come.
所以 = so
因为天天吃羊肉，所以不想吃了。
Yīnwèi tiāntiān chī yángròu, suǒyǐ bù xiǎng chī le.
Because I eat mutton every day, I don't want it anymore.
paired
3. Share a tip
Put the 因为 (cause) clause first and the 所以 (effect) clause second — you can drop one, but never swap their order.