You just get a tripod,  go to manual mode, set your shutter speed to 10 seconds or more,   Take a test shot (ISO 400 setting should be fine) ,  Adjust your aperture if the shot is too overexposed or underexposed.  Keep testing to you get the shot you want.

Keep in mind that if you are trying to do this during the day, you will have to take your ISO all the way to the lowest setting (100 usually) and your aperture all the way up f/22.   If it is still too bright, you will have to put one or more ND filters on your lens to let even less light in.

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