add precommand for some commands and trim space.

README.md

@@ -578,14 +578,14 @@ The result should be like this:
 nestedVirtualization=true
 ```
 
-Go into your WSL distro (Run `wsl` in powershell) and check if KVM is enabled by using the `kvm-ok` command. The output should look like this:
+Go into your WSL distro (Run `wsl` in powershell) and use the command `sudo apt install cpu-checker` and check if KVM is enabled by using the `kvm-ok` command. The output should look like this:
 
 ```
 INFO: /dev/kvm exists
 KVM acceleration can be used
 ```
 
-Use the command `sudo apt -y install bridge-utils cpu-checker libvirt-clients libvirt-daemon qemu qemu-kvm` to install it if it isn't.
+First update apt `sudo apt-get update`, then use the command `sudo apt -y install bridge-utils cpu-checker libvirt-clients libvirt-daemon qemu qemu-kvm` to install it if it isn't.
 
 Now download and install [Docker for Windows](https://docs.docker.com/desktop/windows/install/) if it is not already installed.