Write the idioms and phrases from your list onto index cards.
Organize your cards into categories so that you have a stack of money idioms, relationship idioms, business idioms, time idioms and any other categories you want to use. If you find that you have more than 15 cards in any given stack, subdivide it further. For example, split your relationships stack into a family stack, a friendship stack, and a love and romance stack. This breaks the list into manageable pieces.
Choose one stack of idioms and phrases to practice. Look at the definition of each idiom and guess its origin. Some will be clear when you think about them, like "snowed under" for "overwhelmed," while others will be less obvious, like "a piece of cake" for "easy." For the harder ones, invent an origin that will help you remember the meaning of the phrase. Create a mental picture to go with this origin, and think of it whenever you hear the idiom. For example, for "snowed under," you may picture a man completely buried in snow, with only his hat remaining on top of the mound.
Find sample sentences using each idiom in the stack, and write them on the cards. As with any vocabulary word, using the idiom correctly in context is just as important as remembering its definition. Find your sample sentences by Googling the idiom or looking it up in a dictionary.
Put your cards up on the wall in a room where you spend lots of time, and read them every day for a week. Practice creating new sentences with the phrases each day.
Watch television or movies in the language you are studying, and listen for the idioms you are learning. When you hear one, note how it was used and check the usage against your sample sentences to make sure you are practicing it correctly.
Work on the stack of cards in this way for a week, then take the cards off the wall and begin with a new stack. Keep the cards you have learned, and review them periodically to ensure that you remember them. Underline idioms you have learned when you see them in books, magazines or newspaper articles you are reading. This will keep them fresh in your memory and remind you how they are used.