The posts links in WordpPress are generated automatically,it depending on the post title and permalinks settings.
If you want to change slug of your post, You should perform the following steps.
1. First Open WordPress admin panel and open the Posts tab.
2. Second is select the post you want to edit.
3. Using the Screen Options tab at the top make sure the Slug block is enabled.
4. WordPress site Slug block contains the post SEO friendly URL. You can edit the value to set your custom URL.
5. When you are done, click the Update button.
6. Now you can check your post slug is updated.