When Coopers falls in the black hole Gargantua and thanks one of four former U.S. Marine Corps tactical robots he can study the singularity of quantum data and collect them.
Then he enters the Tesseract's 5th dimensional space to relay the data to Murph. But how?
Explanation: everything is linked by the strings of time, which Cooper can manipulate. The beings made this comprehensible to Cooper by allowing him to physically interact with the Tesseract.
Every push of a book from him was communicated to the appropriate time period with gravity.
Some informations: the Tesseract is an enormous, hyper-cubic, grid-like structure and a means of communication for the bulk beings (sentient beings able to perceive higher dimensions) to express action through gravity with NASA. The bulk beings can perceive five dimensions as opposed to four, able to see every moment in the past, present, and future. The bulk beings can influence gravity within any of those time frames.