If you don't know how to create a state machine to implement I2C master, you are in trouble. You could try some of the I2C cores at OpenCores.org but understanding somebody else's code is often more difficult than writing your own. And you still have to interface it to your main project.
Since you're trying to do a very trivial application in an advanced device, I have to think this is homework. Nobody in their right mind would code up an I2C controller for a project that could be more easily done on a uC.
OK, now that that's out of the way, you need to understand the I2C protocol and build up a state machine that will send the proper signals with appropriate timing. The datasheet gives you all the necessary information concerning transactions. NXP has a document for the I2C Standard
At the bottom level, you need to be able to control SCL and send a byte plus handle the Ack bit. Then you need to move up a level and implement the 3 different transactions shown on page 12 of the datasheet. Look at the very long time delays required as shown on pages 10 & 11.
The suggestion on the Xilinx site to use a CPU core makes a lot of sense. This could allow you to bit-bang the protocol and this is going to be a LOT easier than creating an I2C core. But it still requires a CPU core and Xilinx provides that.
This is going to be an enormous amount of work for a project that could be done in a few minutes on an Arduino. Maybe put an Arduino between the sensor and the FPGA. Let the Arduino deal with I2C and the sensor while using SPI to communicate between the Arduino and the FPGA. The SPI transaction could contain only the required information. Better yet, use a serial protocol over the UART.
Or, change sensors and use the breakout board from Adafruit:
https://www.adafruit.com/product/3779This board supports UART and that's a lot easier to implement in an FPGA than I2C.
There is no way in the world I would want to get involved with I2C in an FPGA. Maybe if I used a CPU core and bit-banged it... I would not want to code a state machine.