If the quotation ends with a full stop, then the full stop goes inside the quotation marks.
- He said, ‘I love you.’
(I love you is the complete quotation, so the full stop is part of the quotation.)
If the quotation doesn’t end with a full stop, then the full stop goes outside the quotation marks.
- He described the woman as ‘stunning’.
(Stunning isn’t the complete quotation, so the full stop isn’t part of the quotation.)
It is the same with question marks and exclamation marks.
- He said, ‘How can I love you?’
(The question mark is part of the quotation.) - Did he describe the woman as ‘stunning’?
(The question mark isn’t part of the quotation.) - He shouted, ‘Don’t jump!’
- I can’t believe he said she was ‘stunning’!