1. Open problemset and search for greedy problems, with solution and rating.
2. Choose the easy ones 1000-1200
3. Try to figure out solution, if you failed to do it in 10m, read solution given by author.
4. Try to implement solution, that you figured out/read. If you failed to do that in 30m, read implementation of autho. Try to understand why it works, and then try to write your own implementation again.
5. Once you solved 5-6 problems of rank 1400, without looking at solution, you are done. Else return to step 3 with new problem to solve.

Bonus: Try to read and learn algorithms listed here: https://www.geeksforgeeks.org/greedy-algorithms/

Check out -->

1] https://www.hackerearth.com/practice/algorithms/greedy/basics-of-greedy-algorithms/tutorial/ [Basic Tutorial for Greedy]

2] https://www.a2oj.com/Category56.html [Questions from Beginner to Advanced]

Adding to the comments, also try solving questions of tag constructive algorithms, it really helps in training your mind to prove your thesis, and most of the time, the solution is simplified to a simple greedy approach.

I always had problems with greedy algorithms, I would say that to use them you need that your solution make sense in your head, if it doesn't, I would say to just run away from them.