Write "concur" on a note card, along with sample sentences using it, in order to help you memorize its meaning. Look it up in the dictionary to get its definitions and pronunciation. Some examples of its use might be: "Her employer would not concur with her actions" or, "The student concurs with the result of the exam" or, "I concur with this statement." You can find others on the Web. These examples can help you get a better understanding of the word.
Memorize the definitions of "concur" in order to become more confident about using it. You can refer to your note card when necessary. It might take you a day or a week to get comfortable enough with "concur" so that it starts coming up in your sentences. Keep the card with you for the first couple of days so that you can easily pull it out and double-check its meanings.
Begin to use "concur" in your daily conversations with your friends or coworkers. The best way to learn something is by using it or teaching it to others. If someone hears you say it and asks what it means, you'll have an opportunity to do both. After a while, "concur" will become a regular part of your vocabulary and you will no longer have to think about whether you are using it correctly.