Here's a video of someone putting the sim card in. Let us know if this helps

It did help!  Now it seems there’s a problem with how I inserted the SIM card (the red lights are flashing) and I can’t figure out how to get the card out (I’ve tried using tweezers, but I’m concerned about damaging the card).  With a phone, the entire tray pulls out, but this tray doesn’t seem to budge!

Oh there is no sim tray with these 

If I remember correctly the sim slot is spring loaded so if you just push inwards on the sim card it should pop out enough for you to remove.

It won’t move and I am concerned about damaging it trying. 

Are you using the smallest SIM card? There are three different-sized SIM cards. The hub uses the smallest of the three, a nanoSIM card.  

If the edge of the SIM card is exposed, attach a small piece of adhesive tape over the edge of the SIM card. If the adhesive tape is strong enough, this may be all you need to extract the SIM card. If using metal tweezers, a set of plastic tweezers is recommended. There’s less of a chance of damaging the SIM card. Make sure the hub is powered off and the backup battery removed when extracting/inserting the SIM card.

Precision Tweezers | Amazon Canada

There is a small symbol of a SIM card stamped into the plastic just below the SIM card slot showing the orientation of the SIM card. When inserting the SIM card into the slot, the angled cut-out is on the left side and the brass-coloured contacts face downward.