Step 1: Run the following command to create a migration file.
        php artisan make:migration alter_users_table
        (here users is the existing table name)
Step 2: Now check your application. 1 migration file is created in path database/migrations.       
        The file name is like : 2018_09_10_102106_alter_users_table
        Here we will add 1 'user_type' field to users table. 
        Open that migration file and write the following in up() function.        
         Schema::table('users', function($table) {
Step 3: now run the following command & check your table. user_type field is added to your table.
             php artisan migrate