Filling the UPSC application form begins with visiting the official UPSC website to access the online application portal. Aspirants need to register by providing basic personal information, followed by filling out detailed sections about educational qualifications, work experience, and personal details. Uploading scanned documents, including a recent photograph and signature, is also required. The form must be submitted along with the applicable application fee. Once submitted, candidates should download and print the confirmation for their records. It’s essential to double-check all entries for correctness before completion.