We can help with specific problems, but can't educate you on the entire concept of Single Server model simulation.
Simulation will differ by what model is used...
Service time distribution - Exponential/Constant/Generally Distributed.
Waiting Room/Queue capacity - Limited/Unlimited
Do a quick google search and you will find academic papers and some Youtube tutorial on the subject.
Oh, you may want to read up on Erlang traffic model as well.
Edit: To start off, search for Erlang C model. This uses Constant for Service Time, and unlimited Queue/Waitroom capacity and probably is simpler model to simulate. This model can be used to predict what percentage of the customers are serviced within given time threshold.