First of all you should be able to determine exact type of the difficulty that your child is facing in learning or attending school on daily basis. You as a parent are most likely to be aware of it because you are in contact with your child since birth and know what sorts of difficulties they have been through while growing up. For example, they are unable to speak, do not understands things too quickly or have any other difficulty.
Next step for you is to determine the type of help you require from the state. This can be done through help from the child's school. For example, the child might need an assistant, if they are unable to manage their stuff on their own, and need continuous help. The doctor's advice in this regard is also important, as the child is most likely to have been referred to them for solution of these problems.
You should then know about the rights of your child for assistance in health services and education. The state is bound to help your child in their difficulties and ensure that they take part in the daily life activity, including education, as much as any other citizen of the country. You can exercise this right anytime you want and if the state refuses a timely special education help to your child, you can even sue the authorities.
Once you have determined the type of help you require for your child, know about the procedure how you can make an application for this. Generally, social or child welfare department is the agency where you can apply for the special help for your child and this has to be done through a proper application process. Also, know the documents you are required to attach with the application and make sure you fulfil all the necessary requirements at the time you make an application for help.
Then is the actual process of making an application, and wait for its processing. You might also be interviewed by the social services or else asked to fulfil other requirements i.e. submission of more documents. After doing that you will have to wait for some time before your child starts getting help.