Apple ID verification code is required. It says to enter your Apple password Followed by the verification code given on other device I do but it still says not recognizable

Trying to set up iCloud on a 2011 Mac pro that somebody gave me I cleared out what I thought I was supposed to clear but now won’t let me sign in with iCloud.Keep saying to type password followed by verification code I have done this but it still keeps saying unrecognized Apple ID and then if I put in Apple ID and password it gives me another verification phone an iPhone and I enter that but still doesn’t work what am I doing wrong I see no spot for the verification code like a little black **** I normally get an iPhone