Pruning a plum tree

[Mrs A]

Hello

I bought what I thought was a container grown victoria plum tree the other week but when I came to plant it it turned out to be bare root - I only planted this this weekend and know you're supposed to plant bare root fruit trees from Nov - March - do you think it will be ok?

We've staked it wrong as well I think but it's tied securely so I reckon it should be ok.

And I have no idea how old it is. How do I prune it? Do I do this now?

Picture attached (I think)

Thanks!