For your child to enter the UK and stay for more than six months you will require a Settlement Visa. A Standard Visitor Visa (LINK TO PAGE 14) is fine if you want to stay for less than six months.
To apply for a Settlement Visa your child must have a parent living permanently in the UK who is either a British Citizen, has settled in the UK, or who has asylum or humanitarian protection in the UK. It usually takes about 12 weeks to get a decision and you have to pay the health surcharge (which entitles you to medical treatment from the National Health Service). They may be able to extend their visa and settle in the UK permanently (Indefinite Leave to Remain).
If you apply through MyUKVisas, we will help you present the best possible case so you have the highest chance of success.