Your intelligence Quotient or IQ score is important to secure a job, an admission or win through a like situation. However, you can't equate your IQ score with intelligence. Later includes emotional intelligence as well.
Now your question, "Is having a high IQ necessarily mean you're going to be successful?"
In one word NO...
It is not necessary to have a high IQ score to be successful in your life. No doubt some level of intelligence is necessary. But there are other important factors:
First, you need clear goal. Without a clear goal you are going nowhere. Suppose ten people are going to New York, ten others to to Boston and ten to Singapore. You also want to go somewhere... but where?
Second, you need some effort/work (smart or hard depends upon you) to achieve your goal. Going back to our example, you want to go to New York from Singapore. You need money, you need air-travel tickets, you need to know your route towards Changi airport and you also need some reservation at New York for the minimum. You need to work that out. If you are going to spend your vacations then you need more money. You have to collect the required amount of money and fulfill other requirements to go to New York.
Third, you must be persistence in your effort toward your goal. Your effort does not require you to work day and night and so hard that you fall ill. Instead you should work on daily basis to achieve your target, however little it may be.
These are simple three principles that can make you successful in any field of life. I repeat again:
