Just a note for you as a new 800 user, when shooting in TTL, be carfeull with the BL mode. It is known that the flash behaves weirdly when using light adjustment (+ or -). It is usually fine to use "simple" TTL without the BL. Try it and make your own conclusions, it might be slightly different!
Using BL and adjustment is kind of confusing for the flash, it's like asking the flash to manage how it should be and telling it how you want it to be at the same time! To avoid the dilemma for the flash, in practice, it might be better to avoid BL when using adjustment.
One thing for sure, the result might be fine, but it won't be consistent! Just be careful!
As well, the best simple advice I received for this flash is:
Use TTL + BL outside, use TTL inside (no BL inside!) and let the flash do its magic!
Just play with it, practice, adjust, reshoot, revise, etc. and you will find your way very quickly I believe!
Good Luck!