Maybe it's just me, but still not certain how and where to add keywords in Pinterest. I've been adding them at the end of descriptions (#key1 # key2, etc.). But I don't see such keywording on other pins, so think I'm missing something.
Some places you can add keywords to are:
1. Your profile name & bio
2. Board names/descriptions
3. Pin Titles/descriptions
4. Text overlays on Pins When using keywords, write them out in sentences or phrases rather than listing them out as single words (this is known as keyword stuffing and is advised against).
Think about what words or phrases your audience will be searching for and use them in the places I mentioned above. This will help you and your content show up in search results.
Hope this helps!