I need to make a world map on a wall with small led lights to show some cities, can somebody help me with this project?

I have a world map on the wall and I need to put a small led light (3mm or less) in many cities of the map, using different colors.
I have NO idea how to do it, actually I don’t know anything about electronics, so I need like a completely beginners step by step guide, something like “dummies” :- )) Also I might need to add quite lights in a future, so I need to do something that can easily grow in the amount of led’s needed. I am sorry my English is not that good, hope you understand my needs.
I don’t know what kind I need to get, how to connect each one, what power, etc.
Any idea or any help will be kindly appreciated.
Thanks a lot!

If you just need the LEDs to on constantly, the circuit required will be very simple.
The required circuit would consist ony of a DC power source, a current limiting resistor, and the LED itself. The resistor value to use will depend on the voltage of the DC power supply, and the current requirements of the LED. Common LED colors are red, green, and yellow, but white and blue are also available.

Just to throw out some ballpark values, if you used a 9 volt battery for your power source, and the LED has a forward voltage drop of 1.5 volts, and it required 10 mA to achieve a desired level of brightness, then the resistor needed would be
(9 volts - 1.5 volts)/10mA=750 ohms.

There are many instructables dealing with LEDs, in fact a whole sub category under "Technology". LED circuits are a common starting point for many people just getting into electroics, so there is an abundance of information available here and elsewhere on the web.