If it is earned income, then you will get a form for it. The form tells you where to enter it. If it is not earned income, it may not be taxable. Gifts, for instance, are not taxable, although there are limits on them to keep people from calling everything gifts and not paying taxes :-). Adoption subsidies might come from a non-profit and be considered grants, e.g. gifts, that fulfill a valid social purpose endorsed by the government. For example, people don't pay taxes on the food they get at a food distribution center :-).
Thanks for adopting!