Added passcode info

TopDog.tex

@@ -191,7 +191,16 @@ and write it down on a note in your wallet!
 Now go to
 \href{http://snickerboa.it.liu.se/register.jsp}{http://snickerboa.it.liu.se/register.jsp} and
 register an account, see \cref{fig:login}. Note that the registration link is
-hidden and must be typed just like that.
+hidden and must be typed just like that. The registration screen is shown in
+\cref{fig:register}. Note that registration requires you to type in the correct
+\texttt{passcode}, which is found in Lisam. The passcode is to discourage people
+outside the course to do the lab and appear on the scoreboard. Please do not
+share the passcode.
+\begin{figure}
+    \centering
+    \includegraphics[width=.9\linewidth]{register.png}
+    \caption{The TopDog registration page.\label{fig:register}}
+\end{figure}
 
 Next, return to the login screen and login with your credentials. If you
 succeeded, you will be greeted with \enquote{Let's get
@@ -201,7 +210,7 @@ login username and password before contacting us (see \cref{sec:contact}).
 \begin{figure}
     \centering
     \includegraphics[width=.9\linewidth]{login.png}
-    \caption{The TopDog login page\label{fig:login}}
+    \caption{The TopDog login page.\label{fig:login}}
 \end{figure}
 
 \section{Scoreboard}