I would like to know the step by step guide for connecting DS18B20 with STM32 @ NUCLEO-F746ZG and reading the temperature in pc thru stmcubemx and kiel uvision 5. Being a beginner , i find it very tough to find tutorials explaning this.

[Rstua.1]

Being a beginner, it may be very difficult to use st.com hardware. There are plenty of st.com sensor & processor & development-board combinations and not all combinations are represented by st.com example software. Further, not all st.com example software are from the same vintage. For example, a particular solution my contain it's own st.com hardware abstraction layer which may predate the more commonly used st.com hardware abstraction layer downloadable from the st.com's github.com account.

As the DS18B20 is a Maxim part, it is unlikely you will get help here. I would recommend using one of the stack-exchange site for technical help (https://stackexchange.com/sites#). Beware, there are dozens of stack-exchange sites. Take care to pick the correct one. Always attempt to try something before asking. Never ask for an opinion. Always only ask 1 well formed question at a time / per post.

Also, you might explore the adafruit.com web site and forums. They appear to sell STM32 processor based products ( https://blog.adafruit.com/2019/09/30/coming-soon-adafruit-feather-stm32f405-express/) as well as the DS18B20 (https://blog.adafruit.com/2018/08/17/new-product-high-temp-waterproof-ds18b20-digital-temperature-sensor-3m-long/).

[Tesla DeLorean]

That's really not how things work, you can't pick very specific hardware combinations and expect someone to have done all the hard work for you already. Focus on understanding the underlying technologies, find examples that are available for the DS18B20 and port them to the platform you have chosen. The part almost certainly has data sheets or manuals explaining operation which can then be applied universally.