Make sure that when you clear up after the pup, you use a cleaning brand specifically for cleaning up after dogs - other products may contain ammonia and therefore send a message of "it's OK to go here" to the pup

It's best to take the pup out after sleep, meals etc rather than put out, or leave out, as the pup won't be sure why it is out there and also you will miss a good opportunity to praise for good behaviour.
Do you try giving a little treat as the pup goes outside?
Good luck, don't worry it will get better ;)
LIndsay