These are the rough steps I took. Just keep in mind I am also a layman and have done this exactly 1 time 
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Create JLCPCB account (helps with managing files especially since it is not an instant process)
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Go to my file in the top right of the website
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Upload the Gerber file
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Wait like 5~10 minutes to give time for JLC to process the file. You will know when it is done because when you go to my files it will turn into a picture like this:
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Click on the picture and you will be directed to the order screen. You can verify it is correct by seeing the PCB at the top and it should have the PCB features selected like Layers 2, dimensions 132x373 mm, 1.6 PCB Thickness.
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Choose your PCB options (I went with 5 Qty, in Green with ENIG-RoHs and the extra paper between (skip that its not worth it). Everything else in the top section was default
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Choose SMT Assembly (it will not allow you to do this if you choose an incompatible color / finish option). It took me a while to understand this and I made an incorrect assumption so this is an easier for me to understand:
- Green with any coating.
- Red with HASL
- Blue with HASL
- Black with HASL or HASL-RoHs
- Choose the Bottom Side for SMT Assembly (the are no SMT components on the top)
- Add the BOM and CLP (Pick & Place file)
- The next screen shows all the parts.
- There is no PinHeader available from JLC that works for this so it will show up without the checkbox. You want to make sure all the other boxes are checked and it doesn’t say anything like out of stock or short (whatever they don’t have they won’t put on your board but they will still make it for you so double check. SMT soldering all the parts is beyond my still set)
- The next screen shows were they are going to place the SMT components (nothing to do here)
- Save to cart checkout and you are done.
(Took them about 1 week to make the board and a little bit less then 1 week for me to receive it from DHL to the US)
Pin headers I bought from Ebay (just ensure they are surface/smd ones not the through hole): https://www.ebay.com/itm/2x5-10-POS-2-0mm-Pitch-Female-SMD-Surface-Mount-Socket-Header-Pack-of-10/381753113623
Edit: JLCPCB may give you this warning when analyzing the SMT components on your order. I didn’t have any problems with the key it mentioned D15 14th key in the top row.
