"secondary vertical pointing menu" item activation


Hi everyone,

I am new to semantic ui. Sorry if this sound stupid but when I include
an element of class=“ui secondary vertical pointing menu” in my html
like in the example:

<div class="ui secondary vertical pointing menu">
  <a class="item active">
  <a class="item">
  <a class="item">

it does not allow me to change the selection (“Home” is selected and I can’t select “Messages” for instance).
Is there something simple I missed?

Thank you very much for any kind of help!

Best regards,