An authorized capital means such capital as is authorized by the memorandum of the company to be the maximum amount of share capital up to which a company can raise its funds by way of share capital. As per Companies Act, 2013 Authorized Capital or nominal capital means such capital as is authorized by the memorandum of a company to be the maximum amount of share capital of the company.
Authorized Capital is mentioned in the Capital Clause of the Memorandum of Association. So if you want to increase the Authorized Capital then you have to Alter Memorandum of Association of the Company. It means you have to follow provisions regarding Alteration of Memorandum of Association.
However, unlike alteration, any other clause in the Memorandum of Association, an increase in Authorized Share Capital does not require a special resolution, only Ordinary Resolution is sufficient.