After cutting trees down for firewood and cutting them up and splitting the logs the firewood needs to dry and cure for a minimum of 6 months to a year before burning the firewood in a wood stove or fireplace.
It's really best to give the firewood at least a year before you burn it so it will burn properly and provide much more heat.
Some species of wood such as oak required 2 to 3 years to fully cure and dry before it will burn properly in your wood stove or fireplace.
But for most other wood species 6 to 12 months is a good amount of time to get wood dry enough to burn through the winter.
You can get a moisture meter to test the firewood for moisture content and see if it's dry enough.