'there are certain set expressions: 올해,작년...' - chin.billy.leung
Yup. It's best it is to learn those expression, just keep in mind 해 and 년 stands "year".
E.g.: 새해 - new year, 그해 - that year, 올해 - this year, 작년 - last year, 금년 - this year, 내년 - next year, 매년 - every year.
Beside this the only way is to study text or conversation to fully grasp when you can use 해 & 년.
Just gonna add that 해 is used with pure korean numbers and 년 with sino-korean