Determine what type of plate armor you want to wear. Generally speaking there are 3 types of plate armor that are designed for different situations. Combat armor is smooth enough to deflect weapons. It is made from lightweight armor and has increased maneuverability. Parade armor is for court and special events. The armor itself is weaker than combat armor and heavier. Jousting armor is the heaviest of the 3 armor types. It is designed to provide maximum protection on the jouster's left side and does not offer much mobility for the wearer.
Put on undergarments such as a padded or quilted jacket. You can also place a heavy leather coat under your armor instead of a padded or quilted jacket.
Check your armor for padding. Major armor pieces have padding in them to keep the armor pieces from wearing on one another at overlapping points. In olden times, more padding meant less chance of broken bones during combat.
Put your chain mail on your legs, torso, arms and head. Chain mail is protects the areas that are near the plate armor joints and connections. This adds protection to areas that may be exposed during movement.
Don your plate leg armor. This usually includes attaching your chausses and graves to your legs.
Put your gorget on to protect your neck area.
Add your breastplate and back plate to cover your torso. On your breast plate, attach rondels to provide the chest and armpit area with added protection. Add spaulders to protect your shoulders and vambraces to project your arms.
Put on your helmet and gauntlets. Check your armor for comfort. Work out any kinks or uncomfortable spots while dressing, instead of waiting.