timeNow(){
    echo "$(date +%r)"
}
PS1='[$(timeNow)] \\u@\\h:\\w$ '

It will give you a prompt like this:

[05:34:37 PM] user@Host:/path$

Notes:

• Make the changes in ~/.bashrc or /etc/bashrc or ~/.bash_profile or ~./profile file (depending on the OS) and save it.
• Run source ~/.bashrc (distro specific) after saving the file.