Writing to a Siemens PLC tag

I’m new to Ignition and I’m trying to to write to a tag on a PLC that I’m using as a test
we have 2 servers one for tags and one for projects
I can force to change the tag value on the tag designer but no in the project designer
do you know if or how can I do this
basically I want to write to a tag to change the value of it based on a value change of multiple tags
per example I have a label that change color and text based on the value of a expression
if A = true I want to write true to B