Begin with finger play. Get a "Lube Tube" aka Lube Shooter and take a shot or two of your favorite lube (I prefer Coconut Oil) into your rectum. You'll be surprised how quickly your anus will welcome penetration; if properly lubed.
Fingers and lube are a great start. However it will not be long before you want more. That is when you have to start thinking about safe materials like silicone, steel and glass - anything you should avoid - or plan to use a condom every time. Silicone lubes are great - but you can't use them on silicone toys - so you have to go water based - or our preference which is oil-based (Yes link)
I have also found that tapered toys are great for helping you learn to accept larger toys. A 1" plug is too small - start with about 1.25 - it shouldn't take long to be wanting a 1.5". At that point you can start to experiment with other dildos - realistic or not - your choice.