I’d recommend to avoid aliasses at all - at least until you get more familiar with PowerShell. Instead of using aliasses I’d use tab completion. It reduces the letters needed to be typed as well but it is less error prone and helps maintaining a better style. You should avoid aliasses in general for scripts or when you’re about to show some code for others like in forums.
The actual command PowerShell runs when you use the alias dir is Get-ChildItem. And for help it is Get-Help.
So the proper command for you would be:
Get-Help Get-ChildItem -Examples
Other useful parameters for the cmdlet Get-Help are -Full or -ShowWindow or -Online.
To see the full list of possible parameters you can run