I had seen quite a few tutorials for making a mason jar soap dispenser, and it didn't seem very difficult. The hardest parts were probably cutting the lid of the mason jar to accept the soap dispenser pump, and figuring out where to cut the pump pieces themselves to make them fit in the size of mason jar we wanted to use (which was a pint jar).
This pump isn't the same one that I have, but it shows the parts clearly. For our pump we had to cut the majority of the threaded piece off. That is what stretches between your counter top, down to the plastic soap holder below (we didn't need that part, since our soap holder was going to be the pint jar).
To punch the hole in the top of the mason jar lid, use a hammer and chisel. Also use a block of scrap wood to protect your work surface. Use a marker to trace the size of hole you need, then punch your way around. Be careful not to cut yourself.
Spray paint your lid and ring to match the color of your soap dispenser. We were lucky to have leftover oil rubbed bronze spray paint from another project. I used two coats.
Cut the straw to length. You want it to be cut on an angle so that the bottom tip hits the bottom of the jar. This will allow it to get the last of the soap out (if you don't refill sooner). If it doesn't go to the bottom, you will always have a little bit of soap at the bottom of your jar that never gets used.
When the paint is dry, you can put everything together. My soap dispenser came with a piece that screwed into the top from below the mason jar lid. If yours doesn't, you'll need to break out the glue gun to glue the lid to your pump. Then fill your jar with soap, place the ring over the top and screw it all together.
Also, take note that if you use two different kinds of soaps, they don't really mix together. :)