And how do you worship a phallus? A Holy phallus?
The same way you worship anything else. With pure devotion. You touch the base, kiss the head, caress its length, light candles, and offer rice, flowers, or fruit to it. Let the artist in you rub red ocher onto its surface. Or if you are all out, perform the abhishek--the bathing of the lingam with milk, or water, or yogurt, or ghee, or honey. The possibilities are endless.
And what does the Phallus worshiper get in return? Concentration of the mind; help to communicate with god Shiva; an uncanny ability to focus their attention, which is to say, to rise above body-consciousness.
That's why each lingam has its yoni--the feminine vessel, a representation of the feminine generative power, and symbol of the goddess Shakti.
So, there you have it. A god and a goddess. A lingam and a yoni. The masculine and the feminine generative powers of and in nature. And what a better place for a lingam to be than inside a yoni! Shiva's organ is depicted in communion with Shakti's sex; their union representing the eternal process of creation and regeneration.