Visa Appeal

Please how do we appeal to an Irish visa decision of refusing a woman to join her husband with her children.
Also how do we write an appeal letter to this decision

The appeal process is fully explained in the refusal letter.

The process differs in each country, so there’s really no point asking a broad question like this here.

You need to read your refusal letter and address every single refusal reason given to you in the letter, give your justification and argument for each point, write your appeal letter and send it away according to the way specified in your letter.