To create a new virtual machine (VM) using a qcow2 image file in KVM, you can use the following steps:
Install KVM and the associated tools, such as virt-manager and qemu-kvm, on your host system.
Start virt-manager.
From the main menu, select "File -> New Virtual Machine".
In the "New VM" wizard, select "Local install media (ISO image or CDROM)" as the installation source and click "Forward".
In the "Storage" step, select "Customize configuration before install" and click "Forward".
In the "Virtual Machine Details" step, enter a name for your VM and select the desired memory and CPU configuration.
In the "Installation Destination" step, select "Local disk" as the storage type and click "Forward".
In the "Storage Options" step, click the "Add" button.
In the "Add New Disk" dialog, select "Create a new disk" and choose "QCOW2" as the disk format.
Click the "Browse" button and select the qcow2 image file that you want to use as the disk for your VM.
Click "Finish" to create the new VM with the qcow2 image file as the disk.
Start the VM by clicking the "Play" button in the virt-manager interface.
Note: These steps assume that you have already set up a KVM host and have the necessary permissions to create and manage VMs. If you have not yet set up a KVM host, you can refer to the KVM documentation for instructions on how to do so.