First box has 14/2 from panel, 14/2 to outlet, 14/3 to the other switch
Second box has 14/3 from the first switch and 14/2 to the light.. how can I wire these up for 3 way switch.
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Here's the headache. Cables are color-coded to distinguish wires from each other. They're not color-coded by function, which makes 3-ways super confusing. We're gonna fix that. Get a common 5-pack of colored electrical tape.
There is only one /3 cable. On both ends of that cable, tape both the red and black wires yellow. Yes, really; both wires get marked yellow. They are travelers, and they are interchangeable.
Over in the second box, with the cable to the lamp, tape its black wire red.
Now your wiring looks a lot like this
Buy about couple feet of /3 cable that same size (or #12 if you don't know the size). From this we will make pigtails. You can also just buy 8" lengths of black, red and green #12 solid THHN if you'd rather.
On one 3-way switch, identify the black screw and put a black pigtail on it. On the other 3-way, also on the black screw, put a red pigtail on that. You could use another color and mark it with red tape.
Oh, almost forgot the grounds (safety earthing). I tend to ignore them, even though it is vital to hook them up, and do them first. So -- also, put bare or green pigtails on the ground screw of each switch. Either color is fine, they are equivalent but the green is less likely to short against stuff because it's insulated.
The 3-way switch with the black pigtail goes in the first box (with supply). This will be obvious in a moment.
In both boxes, the yellow wires go onto the brass screws on the 3-way switches. Join all the bare and green wires with one wire-nut and shove em into the back of the box. Join all the white wires to each other with one wire-nut, and shove em into the back of the box. Then do all the black wires similarly, then all the reds. And you're done.