Hi David and welcome to the forum!
For portamento to take effect on your playback you have to update your Sibelius Playback dictionary. Go to Play/Dictionary/Staff Text and add the word portamento. Effect: Sound ID change "+portamento" Until next sound ID change.
You can also add this command to the portamento line. Go to Play/Dictionary/Staff Lines/Portamento and add Sound ID Change "+portamento" Until end of last note under line
Take a look at the readme file that came with your sound set. There are some recommendations what else you might want to add to your dictionary.
If you want a muted trumpet in your score, please create two trumpets with different channels on the Playback Devices/Manual Sound Sets page. One time choose "Trumpet" and one time choose "Trumpet mute". In Vienna Ensemble load the appropriate matrices on the same channels you set on the Manual Sound Sets page.
To switch from the "normal" to the muted trumpet, create a Technique Text in Sibelius with the command "mute" or "con sordino". To switch back write "ord.", "normal" or "senza sordino".
Tremolo automatically works with the symbol where 5 lines cross the stem. If you want it also with 3 or 4 lines crossing the stem, make the following change in your Playback Dictionary.
Go to Play/Dictionary/Articulations/16 tremolos (and 8 tremolos) and add the Sound ID change: "+tremolo.unmeasured"
Best wishes,
Andi
Vienna Symphonic Library