So first things first open up your Instagram app and find the picture you want to embed.
Remember your account must be public!
This is one of my uploads to the miniminsdotcom account. Now at the bottom right there is 3 dots tap that.
This should appear on screen.
Tap copy share URL...
I have been playing with Instagram and I have noticed that it is easy to post links but it is difficult to follow them (you cant click on them, you can copy them).
So I created a really simple system to make really short links for MiniMins posts.