Well it depends on a couple of things, mainly the harmalas and how you want to go about incorporating them into the blend.
The first option is to use extracted harmalas while the second option is to make a menstrum.
If using extracted harmalas, dissolve 250mg - 400mg of harmalas in methanol in a shot glass. (I use HEET from the automotive section. The yellow bottle is methanol and the red bottle is pure IPA) It can take awhile for them to dissolve, so be patient and keep stirring.
Once all of your harmalas are dissolved, add 1g of spice to the harmala/methanol solution.
Once that is dissolved, add 1g of leaf matter and allow the solution to evaporate.
Once everything is soaked up and starting to dry, move it to a baking tray so that it can fully evap. I like to stir it up quite a few times just to make sure that all of the methanol is fully evaporated. Once you're confident that it's good to go, smoalk a bowl. Start off slow and ease into it.
For making a menstrum, take 10g of caapi leaves and soak them in ethanol, IPA or methanol for 30 days, shaking lovingly at least once per day. After 30 days, filter and dissolve 1g of spice into the menstrum. Now evaporate this onto 1g of fresh caapi leaves and do the same dry out process.
A lot of people use mullein as a base herb because it absorbs everything so well. Feel free to choose a blend that you like the most. The options are pretty limitless.
I hope this helps and good luck
Edit: As far as how to smoke it, check out
this thread. The verdict is, there is no wrong way to enjoy changa!
Convert a melodic element into a rhythmic element...