resetting or loading new sketch

i'm new arduino , tried first project today. uploaded script  "blink" arduino uno , worked instantly. tried change duration of blink, , can't seem load new code in. tried closing old sketch box, re-opening it, renaming it, , think of. uno runs first script continuously, , can't reset button. tried pressing reset on uno usb cable connected, unplugging , re-plugging, , kinds of other ways reset. when try load new sketch, info bar @ bottom of sketch window says "uploading..." while stalls green status bar filled, , gives message "problem uploading board"
wow -rb

go preferences , and check box "show verbose output during: [ ] compilation [x] upload".  try upload again , if meaning of messages not clear, report them here , maybe can tell why failing.

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