What are the conditions for polygyny?

Islam has permitted a man to marry from one to four women, provided he possesses the financial and physical capability and does not fear injustice. Allah Almighty said: (But if you fear that you will not be just, then [marry only] one). So, whoever fears injustice should be content with one. If a man has the ability to marry four, he may do so, and if he is unable, he should limit himself to one. Therefore, there is no harm for someone who finds himself capable of marrying more than one, and that might be better for him.