There are many methods of projecting which means you have to use the one you find the most comfortable and safe.
In astral projection the astral body leaves the physical. The astral body is one of seven sheath bodies we all have - as we are all multi-dimensional. These bodies include the physical, mental, causal, etheric, emotional, spiritual.
What I have found is that some people can astral project naturally - and have been doing it for years. Other people are afraid to leave the physical body and struggle with it, never being able to astral project. These people could try remote viewing as an alternative.
You travel out and are aware of things you encounter along the way. To astral project, as with all out-of-body experiences one must feel totally relaxed.
From there you use the projecting technique you've settled on. I recommend to focus on your breathing. Using some breathing techniques does help the process. The subject has been massively covered so start looking up astral projection techniques or try to develop your own one.