Tap the Delete Message button in the pop-up menu (earlier variations of the iphone might have a little various options in the menus, but they're comparable enough that it shouldn't be puzzling.
Kpatụ bọtịnụ Ihichapụ ozi na nchịkọta nhọrọ (mmalite nke iOS nwere ike ịnwe nhọrọ dị iche iche na menus, ma ha yiri nke ahụ ka ọ ghara ịdị mgbagwoju anya.