For me, that looked like understanding past trauma, and then doing the work: meditation, journaling, fixing diet and exercise, sleeping better, and enhancing existing relationships with friends and family.
Then, I felt more comfortable knowing myself and being my authentic self. With that foundation in place, I put real energy into expanding my communities. I put myself out there. I asked people to hang out, and I shared my struggles. I was more comfortable being vulnerable.
There are other tactics that have worked. I introduced like-minded people to one another and let those connections grow on their own. I spend time on touching base. When I read an article or see a tweet that a distant friend might enjoy, I send it. And ask how they are doing. I lean into curiosity about others. Ask people probing questions about their lives, hopes, fears.