You need to draft or have an advocate draft for you (if you can't afford to hire one) several documents that usually initiate proceedings in such (civil) matters.
Once these are filed in the Children Court, they need to be served upon the respondent (father) so that he too can file his defense/response.
Then case will be set down for hearing. If the father denies paternity, a DNA test may be required for proof.
At a small cost I might assist