My training was a week long, about a day and a half or so of basic HR/office environment/team building type things, and then 3ish days of SALT-specific training (tax software, research websites, etc). They expect you to know nothing coming in, but do take really good notes about what you learn.
If you get an internship, you “onboard” for 3 days in the office where you will be interning. You get your computer, other materials, ID card, and will do some trainings about the software that you will use as a KPMG intern. Then, the following week, you will fly to Orlando and go through a week long training with interns from all across the U.S.- it’s super cool. This training is more in-depth and focused on eAudit, which is the audit software that KPMG uses. It’s a great opportunity to network with interns from all across the U.S. (your roommate will also be another intern from another office). Don’t worry if you don’t retain much, though- you will learn most of what you have to do on the job, not at training!