How do i make a push button work like a switch in PLC ?

by applying latching principle 

Apply latching method in ladder program

Use Set/Reset memory bit or Latch

Make a XIC contact input, with a "OneShot" Latch Output IF XIC is closed.

And, IF Output is ON, on next pressof XIC, with a "OneShot" Unlatch it

one have to use combination of rising and falling edge switches , memory register and also latching concept

In parallel to the push button take the feed back of output which is activated through this push button.

By using POS (+ve edge detection) along with SET and RESET coil!

BY USING LADDER LOGIC DIAGRAM OR LATCHING METHOD 

By applying latching method, i.e addding a sub rung to the main rung with an input variable that is labeled with the same label of the output so that once you click on the pushbutton you will activate the output, and because the output coil is activated the input holding the same output label will be also activated and so your output is still holding the state even your pushbutton is zctivated only once.

By using contacts in PLC ladder logic 

a ladder program will be used to make a latch contact