I think I have installed my new rear deraileur incorrectly, can anyone give me some advice
From your picture, there are a couple of questions.

Is the B screw in the correct place.
Is the chain the correct length

Please watch this video on installing a deraillieur and 1 minute in, they mention the B screw and it's corrct position. Note the two different types of fittings, the direct bolt to the hanger, and the bolt to the tab and then to the hanger. The video shows both methods.
Or update the question with close ups of the area where you attached the derailleur to the hanger.
You didn't mention whether you replaced the chain too. If you did, please make sure it is the correct length. These links discuss more on chain length.
Chain length link 1
Chain length link 2