Setting up new iMac

I Purchased a iMac about 4 weeks ago and Apple will not let me sign in they don't recognise my password and i do not receive there emails after they have said there on the way they also do not recognise my DOB. Being new to Apple and the wrong side of 70 i don't no where to go from here.
I look forward to replies Kind Regards alfiegeorge

Is this a brand new iMac…or used ("new to you")?

- Nick

To follow on from Nick, do you have an Apple ID whichb is a requirement to enter th App Store for updates etc. To change Apple ID password have a read of this:-

Apple ID: Changing your password - Apple Support

If you do not have an Apple ID have a read of this link:-

https://appleid.apple.com/account