Do I need to be sitting at my computer for lessons/classes at a certain time?

No. Lessons are pre-recorded for your convenience. You have 24/7 access to them. We often create brand new modules and lessons. When we are creating a new class (1 to 2 times per year) we release new lessons weekly and send an email when it's ready. 

We do host a "live" member meeting once per month. We record that in case you miss it. 

And for the public, Wardee does a live #AskWardee podcast each week on Wednesdays (except summer break). That is also recorded and transcripts/recordings can be found at AskWardee.tv.