Any video tutorial for 3D printing
[The question ask asked is vague, but since you are new it is understandable.]

If you want to build a precision prototype then you have to decide on the level of precision that is necessary. There are different types of 3D printers and services available which give various levels of precision and functionality.

Fused Filament Fabrication/Fused Deposition Modeling - This is typically a means of producing functional prototypes using plastic filament. In terms of precision it is currently the lest precise, but the most cost effective.

Binder Jetting - This is basically crazy glue with food coloring which is inkjet printed onto a white powder layer by layer (vast oversimplification). Useful for producing prototypes with colours for product mockups but not for functional parts. This is mid the mid point in terms of price and precision. 

Stereo Lithography / Photo polymerization  - Lasers cause a liquid resin to harden and stick to each other. Also notable for being the first form of 3D printing, this is the highest precision that is easily attainable. The cost varies based on the provider but it is usually the most expensive option.

Depending on your needs you may find that it is cheaper to develop a single prototype part (just one part not an entire machine) by sending out to a contract manufacturer as opposed to purchasing a 3D printer. 

Here are some examples of what to do when:


If you want to develop a diamond engagement ring for a customer: Send out to a contract manufacturer, for Stereo Lithography
If you broke part of the cupboard and its easy to design a new one: Consider purchasing a sub $400 USD FFF machine and learn to use it.
If you are developing a new line of designer sneaker: Send out to a contract manufacturer for Binder Jetting.
If you are doing miniature figurines for a stop motion animation television series: Invest in a Binder Jet machine and learn how to use it.


In my experience, people don't buy a 3D printer until they have held a 3D printed part in their hand or have seen the machinery in person. If you are new, start with a contract manufacturer and when you start spending so much on them that it is equaling the cost of owning a machine, then invest in your own system.