Wiring 3-way switch (power at light and switches meeting in junction box)
A picture is worth a thousand words. This picture only applies to existing wiring, not new construction.



Here is the link for the picture:
https://www.how-to-wire-it.com/images/3-way-power-at-light2.jpg

If there is an additional box for the light and the power enters there also, then the power white wire would be hooked up to the light, the power black wire would be hooked up to the black wire of the 14/2 which would be connected to the black wire that goes to the switch on the right of my diagram. The white wire of the 14/2 would go to the "hot" side of the fixture and be marked with some red tape and the other end would go the black wire from the switch on the left of my diagram and also be marked with red tape. The travelers should be marked with yellow tape .
If this is new construction, then all switch locations must have a neutral. The cables from the switch boxes to the junction box must be /4 and from the junction box to the light fixture /3. The neutrals can just be capped in the switch boxes.