Find a way to use what you learned.  Things need to be used soon after you learn them. They need to be used again after another period of time.  The more often you use them, the more space there can be between uses and you might still remember them.

There are many things that can act as a natural spaced repetition program.  Reading articles, for example.  The most common words get used over and over.  If you read a lot, some of the less common words will get used over and over.   

First, write everything, new words for example.

Try to write sentences by yourself with those new words.

Repeat, thats the key, to use everything you have learned until it becomes natural.