Choose Keep the character, then name the features that matter to you. For example: "Keep the face, hair shape and original linework from image 1. Use image 2 only for clothing." Add distinctive features such as eye color or an accessory. The starting request also preserves proportions, gender, pose and background.
Suggestions replace the entire instruction. Choose one first, then add your own requirements. Match outfit details emphasizes the garment design. Full-body look also asks for a relaxed standing pose and studio background; use Keep the character when you want the existing composition. Clear empties the text, and edited or empty instructions survive refresh.
For a male character in a dress, keep the request to preserve gender and describe the dress as clothing. Ask explicitly if you also want a gender change. These instructions guide a newly generated edit, so compare the result with the source before continuing.