You have to have gone to the "Wrong side of the tracks", and into "The department of Shadowy Arts and Crafts".
You have to join the guild.
You have to click the trainer to buy the buffs.
Click on your skills menu.
There should be a drop down for your buffs, select one.
there is another drop down that you can select for yourself, or you can select anyone in your contact list, or manually add them in.
You also have to have Mojo Points, and an Instrument. You don't have to equip it, you just have to have it in your inventory.
I mistakenly sold mine, then had to go to the flea market to buy another one. Took me a while to wait for one that I could use, and afford.
Hope that helps
Also, Deandra was correct,

the duration is only for 5 adventures, you just have to cast several of them. So when I got 50 adventures, they cast 10 buffs. However, the duration might also increase as level increases.
