Like all anal sex. Prep and practice. Start small every day and then slowly work up width/girth over time. Be patient. Anal isn't something that you just master and do first try. Work your way up in size but do it daily to get used to it.
I think a lot of the perception of anal sex comes through porn video from studios like Tushy etc. You do know those girls have prepped in various ways sometimes for two days before they shoot a scene, right? One of my ex BFs was like all focused on ass, which was fine because if I'm into you sure ass is on the menu, but I knew that's what we'd probably be doing so made sure during day to plug and stretch, and also before date use an anal bulb to clean myself. If not, it'd be "Sure! Give me 15 minutes to get ready" and then toys/plug first to get warmed up.
Lovense makes the Hush 2 in two sizes, buy both. Start with the small one (1.5" diameter) and only when that's comfortable and easy work up to the larger one.
Practice. Daily.
(Honestly? It's like the first time a dog knots you fully. OMG you can read about it and see it and know what's coming but that won't stop the tears and moans of pain when it first happens. Fuck, amazing now but damn, something you have to get used to. My first I could barely stand afterwards, thought I'd been nearly ripped apart, like have I seriously damaged myself level of what-the-hell just happened. Staggered to my bathroom and both laughed and felt on fire.)