Calling Functions and Stored Procedures

I understand that functions in Postgres server the purpose of both
functions and stored procedures in other db's (e.g., MSSQL and Oracle).
In these other databases, you call a stored procedure with different
syntax (e.g., CALL <procedure name>) instead of using it in line in a
SELECT statement.

My question is this: If I write a Postgres function that is not
designed to be part of a query (e.g., it should just do something), do I
still use a SELECT statement to execute the function? Is there some
other syntax that is the equivalent to CALL or EXEC?

Thanks for your help.