When you drag and drop the Resistor, Inductor, Capacitor components in the Diagram View area, you can see the n-pin and p-pin, colored in blue, on the right side and left side of each component.  Ensure that you have downloaded the correct code files as mentioned in the tutorial.

I have the same problem with connecting the RLC circuit for the file mentioned on the website and I am using version 1.19 of openModelica 

<pre style="margin-bottom: 0px;"><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">In resistor text add ></span></pre><pre style="margin-bottom: 0px;"><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">
</span></pre><pre style="margin-bottom: 0px;"><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">pin p </span><span style=" font-family:'Courier New'; font-size:12pt; color:#8b0000;">annotation</span><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">(</span><span style=" font-family:'Courier New'; font-size:12pt; color:#0000ff;">Placement</span><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">(</span><span style=" font-family:'Courier New'; font-size:12pt; color:#0000ff;">transformation</span><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">(extent = {{-</span><span style=" font-family:'Courier New'; font-size:12pt; color:#8b008b;">110</span><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">, </span><span style=" font-family:'Courier New'; font-size:12pt; color:#8b008b;">10</span><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">}, {-</span><span style=" font-family:'Courier New'; font-size:12pt; color:#8b008b;">90</span><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">, -</span><span style=" font-family:'Courier New'; font-size:12pt; color:#8b008b;">10</span><span style=" font-family:'Courier New'; font-size:12pt; color:#000000;">}})));</span></pre><pre style="margin-bottom: 0px;">pin n <span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(139, 0, 0);">annotation</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 0);">(</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 255);">Placement</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 0);">(</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 255);">transformation</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 0);">(extent = {{</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(139, 0, 139);">90</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 0);">, </span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(139, 0, 139);">10</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 0);">}, {</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(139, 0, 139);">110</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 0);">, -</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(139, 0, 139);">10</span><span style="font-family: &quot;Courier New&quot;; font-size: 12pt; color: rgb(0, 0, 0);">}})));</span></pre>