Multi-currency for payments, moves, etc

Hello team,
I have an issue understanding multi-currency account in order to create a journal entry. My local currency is CRC. I understand I need to select the checkbox to make the entry multi-currency, but let’s assume the following scenario: Customer transfer $100 to pay a debt, the account that will impact those $100 it’s in CRC; the issue is that I want to be able to enter $100 as the amount “paid” to the account in CRC and the system should be able to convert that, but when I type in 100, it converts it 100 CRC, not $100. Am I right on this, or what is the behavior for such scenario? Thank you.

https://erpnext.org/docs/user/manual/en/accounts/multi-currency-accounting

Thank you for your response, but the documentation does not seem to have the details I’m looking for, or I don’t understand. I want to know how the multi-currency in the system address a situation where I want to add $100 to an account that is CRC currency. The system should be able to accept my $100 entry and convert it to my local exchange, isn’t? If so, how I indicate that I’m entering $100 instead of 100 CRC. Thank you and I hope this makes sense.