Symbolize them to place them there

I still try to understand what is symbolize, but can you please let me know if "to place them there" indicate to place/store the keywords in your memory?

While I said earlier that usually, if you learn stuff naturally, 70% will be forgotten. if you put things on locations, usually, more than 90% will be there the next day. Also, it's not just for memorizing. A very interesting aspect is because, by using keywords, you also need to kind of symbolize them to place them there, It's also an interesting tool for text analysis.