I've created a KVM VM using virt-install. There is an image file in the directory /ssd/kvms.
How do I access the virtual machine and turn it on? Do I need to assign an IP address, and if so, how do I do that?
If it's for the same architecture, you can start it with something like
kvm -cpu host -m 1024 -hda /ssd/kvms/my-image.bin
Options
-cpu host
means use same CPU as host machine
-m 1024
use 1GB main memory
-hda /ssd/kvms/my-image.bin
this image is my first hard disk
There are many more options listed in man kvm.
If you used virt-install, you're using libvirt, and you can use virt-manager to manage and view the VM.
ssh -X to your server) to run virt-manager. For the second question, yes, SSH uses the network and so you need an IP address.
What distro are you using? Debian? Centos? Arch? Ubuntu? Suse?
I can recommend http://virt-manager.org/ (older versions can be found in your package manager at your distribution of linux) Very good tutorial can be found here: http://virt-tools.org/learning/start-install-with-virt-manager/
All basic operations with KVM can very easily be done with virt-manager. It is easy, fast and quiet safe for newbies.
All others possibilities how to control KVM can be found here: linux-kvm.org/page/Management_Tools
But i tried some of them and did not working.