If there is no present Custody Order then you want to file an initial pleading for Custody. In your pleading you need to provide some basic information, what you wish to be granted and any special assertions about why you should be granted what you are asking.
If there is already an existing Custody Order then you would file what is known as a Motion for Modification and provide all the information you would provide in an initial pleading but you also must add what has been a material change of circumstances since the original or pre existing order.
You should discuss this with an attorney during a consultation. A knowledgeable and experienced attorney knows what you need to put in your pleading and what the Court is looking for and will also be able to compose a pleading which is persuasive. Custody Matters LLC handles modification pleadings. Custody Matters LLC is dedicated to helping all of our clients get what they want for their children. We take care to find what each client wants, handling all matters of the court, representing in court and helping our clients know what the court wants to see for a strong case.