How to sell bitcoin?

hey guys, I'mnew to this crypto thing and probably I might not know many terms you're using.
So, the thing is, I need to get a payment from a client and they pay me via bitcoin. This was a time when the rate was in tens of thousand dollars. And as the charts have changed, the value has decreased too. So, now I need to sell it.
Can anyone guide me on this?
And oh, i got my account on CoinBase and I'm From Nepal.
Regards