Welcome,

I bring you some portions that explain the event you are talking about, How the miracle happen that Muhammad pbuh could read which before he could not, but he got his information from Allah swt in many forms, dreams, like the ringing of a bell.

Also please reference Sura below:
(Sura 96:1-5)


Sahih Al-Bukhari Hadith - 6.478
Then he began to like seclusions, so he used to go in seclusion in the cave of Hira where he used to worship Allah continuously for many nights before going back to his family to take the necessary provision (of food) for the stay. He come back to (his wife) Khadija again to take his provision (of food) likewise, till one day he received the Guidance while he was in the cave of Hira. An Angel came to him and asked him to read. Allah's Apostle replied, "I do not know how to read." The Prophet added, "Then the Angel held me (forcibly) and pressed me so hard that I felt distressed. Then he released me and again asked me to read, and I replied, 'I do not know how to read.' Thereupon he held me again and pressed me for the second time till I felt distressed. He then released me and asked me to read, but again I replied. 'I do not know how to read.' Thereupon he held me for the third time and pressed me till I got distressed, and then he released me and said, 'Read, in the Name of your Lord Who has created (all that exists), has created man out of a clot, Read! And your Lord is the Most Generous. Who has taught (the writing) by the pen, has taught man that which he knew not.' " (96.1-5).