First of all, I think it is a moralistic ethical thing. That means, nowadays, it is considered immoral to be manly.
Therefore, I think the first step then is unlearning that.
Second step, show and bear more flesh. Super short shorts, roll up your shirt into a crop top, show off your midsection. Wear tank top shirts. Go naked in the sauna. Also, if you’re taking a shower at the gym or anywhere, no need to cover up.
Also, if the weather is good, walk around in public outside with your shirt off. Get a good full body tan.