To alias a command in you ~/.zshrc file, you can use the following syntax:
alias [alias-name]="[command-to-execute]"
For example, it is common to execute the command ls -a. You can alias this command as la as such:
alias la="ls -a"
After reloading the ~/.zshrc file, you will be able to type la and ls -a will be executed.
It is common to have certain folders that you cd into often. If this is the case, you can create aliasses to those directories to make cding to them easier. For example, the following will alias the Dropbox folder:
alias db="cd ~/Dropbox"
allowing you to enter db and change directories to ~/Dropbox.