This is the 16752nd most frequent Russian word.
следовало
"Следовало" means "it was necessary" or "ought to have."
Here, 'следовало' expresses the idea of an action that should have been done in the past, indicating necessity or obligation.
Следовало завершить проект раньше.
The project should have been completed earlier.
In this sentence, 'следовало бы' is used to express a hypothetical suggestion or better alternative action retrospectively.
Следовало бы лучше подготовиться к экзамену.
It would have been better to prepare better for the exam.
This usage indicates realization of a missed obligation or necessity in hindsight.