You are very disappointed, right? How can you keep these words in your mind for long time? The answer is easy — use the words.
How? For example, you can make three sentences with each word. You can write a little message using these words.
If you don’t want to write, you can make a voice recording by using a voice recorder in your phone or any other voice recorder.
You can listen to yourself, or send the file to your teacher or friend.
If you want to learn spelling, speaking and voice recording will be useless.
When I want to learn how to spell a word, I usually take a pen and a sheet of paper and write these words as many times as I need, till I memorize the spelling. It helps the muscles of my hand to remember the movements. When you type, a little bit different mechanism works.
If I want to memorize the word without writing it many, many times but rather just by typing it, in this case I rely on my vision. I look at the word carefully, then close my eyes and try to reproduce this word in my mind with my eyes closed. Then I open my eyes and type the word several times.