The traits are found on equipment (weapons, armor, and jewelry) that you find in the game.
They are random on the pieces you find.

What you need to do is collect equipment then go to the associated type of crafting station for a particular type of equipment (Clothing Station for light and medium armor, Blacksmithing for heavy armor and metal weapons, Woodworking for shields and wooden weapons [bows and staves], and Jewelry station for necklaces and rings), and choose the 'Reasearch' option.

Then select a piece of equipment that has the trait you want to learn. When you click to begin the research, the piece of equipment is destroyed and a timer starts for the amount of time needed to research that trait.

Unless you're looking for something with an expensive trait-- that is, one where the trait material is expensive to buy because it's hard to find-- you can often advertise in zone chat that you're looking for a specific piece of equipment (such as a dagger) in a specific trait (such as Training) for research (meaning it can be white Level 1 gear) and someone might be gracious enough to craft it for you for free.

Obviously, it would be nice if you were to tip them-- but if you're willing to spend money on a piece of gear, you might be better of searching the guild traders for a piece of gear to research instead, because a lot of gear can be bought pretty cheaply from the guild traders. Not only that, but you can often get pieces of set gear for cheap because the set is so common, and when you research the gear for its trait you'll also collect that piece of the set so it gets added to your stickerbook.

Also events like the Dark Heart of Skyrim currently running will fill up your inventory space with random set pieces which you can research. You can deconstruct the pieces with traits that you know and save the ones that you need to research.