im beginner for plc

how to use less than or equal to function in cx programmer

You dont say what versions... but below may help (google)

http://www.proenergo.ru/doc_pdf/soft/CX-Programmer.pdf

https://www.myomron.com/downloads/1...CPIC1-E+CxProgrammer IEC Operation_Manual.pdf

This will also depend on what model controller you are using.

If you provide the model number, we can be of more assistance.

The following introduction guide will get you started in CX programmer quickly.
https://www.fa.omron.com.cn/data_pdf/mnu/r132-e1-05_cx-programmer.pdf?id=1605

Using the less than or equal to function does depend on the controller you are using. Omron will usually use bits that are effective after an instruction is executed. An example would be the instruction Compare. After the rung is executed it will set the following SR bits: equal, greater than, less than.
Here is the CQM1H manual.
https://www.fa.omron.com.cn/data_pdf/closed/mnu/w364-e1-05_cqm1h-cpu.pdf?id=27

Look up 5-19 Comparison Instructions on page 280. It will show you an example.

Hope this helps you out.
Regards,