The stadium grounds has four gates (Sendagaya Gate, Gaien Gate, etc.) from the direction of train/subway stations. This map shows how far each train/subway station is.

The closest is JR Sendagaya Station (440 meters) and Kokuritsu Kyogijo subway station (130 meters).
The stadium itself has eight main entrances from A to H. These main entrances further branch off into smaller entrances such as A1, A2, etc., leading to different floors and seating blocks.
The stadium seating sections are labeled Main Stand, Back Stand, North Stand, and South Stand. Each stand comprise three inclined tiers of seating. The Main Stand is the prime section. Gate F is nearest to the Japan Olympic Museum where the Olympic rings are.