Set the permalink structure in WordPress, Update your permalinks after installing theme. Follow The Screenshot
Or the manual can be changed this way settings for permalinks:
1- Go to the “Settings” section of your WordPress dashboard.
2- One the left side of the dashboard under the “Settings” control, you should see one for “Permalinks.” This is what you should click.
3- Select the method you want to use and click the “Save Changes” button.