How does tubman signal to others that she has arrived
to them?

After Harriet Tubman escaped from slavery, she returned to slave-holding states many times to help other slaves escape. She led them safely to the northern free states and to Canada. It was very dangerous to be a runaway slave. There were rewards for their capture, and ads like you see here described slaves in detail. Whenever Tubman led a group of slaves to freedom, she placed herself in great danger. There was a bounty offered for her capture because she was a fugitive slave herself, and she was breaking the law in slave states by helping other slaves escape. Hope this is the right answer