Headphone out from your computer into your Tascam, assuming it has a line-in.
You'd do yourself a huge favour by forgetting Logic and starting off with GarageBand.
Thousand and one tutorials on YouTube about how to get started, including how to use third-party plugins in it like Analog Lab.
Look through tutorials by Colin Cross the Band Guide, Patrick at The GarageBand Guide, and others.
EDIT: also a very good GarageBand (and Logic) resource that many people seem to forget to look at is the official Apple users-manuals, available online.