How do I get on the train

Hint 1 of 6:

Did you move the sack sitting on the ground in the torture room ?

Hint 2 of 6:

Did you GET POSTCARD that is then exposed ?   +5

Hint 3 of 6:

Did you USE CAD to ANALYZE POSTCARD ?

Hint 4 of 6:

Did you find a microdot ?

Hint 5 of 6:

Do + 46 times, then up arrow 10 times, then + until it's detected.

Hint 6 of 6:

Now you know where the train is.