PHP Notice on activation

I’m getting a bunch of PHP Notices on plugin activation. Starting from this:

Notice: wp_enqueue_script was called incorrectly. Scripts and styles should not be registered or enqueued until the wp_enqueue_scripts, admin_enqueue_scripts, or login_enqueue_scripts hooks. Please see Debugging in WordPress for more information. (This message was added in version 3.3.0.) in /home/c/…/…/public_html/wp-includes/functions.php on line 4138

Notice: Undefined index: addcart in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wp_ultra_simple_shopping_cart.php on line 93

Notice: Undefined index: quantity in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wp_ultra_simple_shopping_cart.php on line 144

Notice: Undefined index: delcart in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wp_ultra_simple_shopping_cart.php on line 163

And when I go to settings, I see this:

Notice: Undefined index: wpus_shopping_cart_collect_address in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 63

Notice: Undefined index: wpus_shopping_cart_use_profile_shipping in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 64

Notice: Undefined index: wpus_shopping_cart_shipping_per_items in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 69

Notice: Undefined index: display_free_shipping in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 70

Notice: Undefined index: use_custom_button in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 75

Notice: Undefined index: wpus_display_thumbnail_in_cart in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 84

Notice: Undefined index: wp_cart_update_quantiy_text in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 94

Notice: Undefined index: display_product_name in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 100

Notice: Undefined index: display_product_inline in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 101

Notice: Undefined index: display_quantity in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 102

Notice: Undefined index: wpus_shopping_cart_auto_redirect_to_checkout_page in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 123

Notice: Undefined index: wpus_shopping_cart_reset_after_redirection_to_return_page in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 125

Notice: Undefined index: wpus_shopping_cart_image_hide in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 127

Notice: Undefined index: wp_use_aff_platform in /home/c/…/…/public_html/wp-content/plugins/wp-ultra-simple-paypal-shopping-cart/wpussc-option.php on line 129

Please advise. Thanks.