Saving related records in laravel

Eloquent's push() saves the model and its relationships, but first you have to tell what you want to be involved in the relationsship.

Since your user-model/table holds the id of the dealership, I assume that a user can belong to only one dealership, so the relationship should look like this:

User Model:

public function dealership()
{
  return $this->belongsTo('Dealership');
}

Dealership Model:

public function users()
{
  return $this->hasMany('User');
}

To save a User from the Dealership perspective, you do this:

$dealership->users()->save($user);

To associate a dealership with a user, you do this:

$user->dealership()->associate($dealership);
$user->save();

Please check this answer to see the difference of push() and save()

You will need to define correctly your models relationships as per documentation If this is done correctly, it should work . This is what push() does :

/**
 * Save the model and all of its relationships.
 *
 * @return bool
 */

    public function push()
    {
        if ( ! $this->save()) return false;

        // To sync all of the relationships to the database, we will simply spin through
        // the relationships and save each model via this "push" method, which allows
        // us to recurse into all of these nested relations for the model instance.

        foreach ($this->relations as $models)
        {
            foreach (Collection::make($models) as $model)
            {
                if ( ! $model->push()) return false;
            }
        }

        return true;
    }

In your case, you have a one (dealership) belongs to many (users)

In your Users model :

class Users extends Eloquent {

    public function dealership()
    {
        return $this->belongsTo('Dealership');

    }

}

In the example above, Eloquent will look for a dealership_id column on the users table. In your Dealership Model :

class Dealership extends Eloquent {

    public function users()
    {
        return $this->hasMany('User');
    }

}

In your store function :

 public function store()
    {
        $user = new User();
        $user->email = Input::get('email');
        $user->password = Input::get('password');


        $user->dealership = new Dealership();
        $user->dealership->name = Input::get('dealership_name');

        $user->push();
        return "User Saved";

    }  

Learn here more about eloquent relationships

Also please take a look at my answer here