1st off you'll need to make the choice of using actual fruit, or juice. With blueberry, you have some options, there's even concentrate you can use. Actual fruit is great, but it takes up space & you'll need to fill that space with something; more mead is the perfect thing to top up with, so you might want to start another gallon batch for just this purpose.
There's also the juice option. Juice eliminates the space problem, but it's tough to know just how much juice is equal to how many pounds of actual fruit, this is the same problem with juice concentrates. That being said, you can make some fine mead/melomel either way.
As for yeast, I'd stick with dry for the time being. The reason being that it's cheap, easy & works well, it also stores well in the fridge. You can also make a starter if you feel the need, but honestly, for a 1 gallon batch you won't need one; just follow the rehydration instructions on the yeast packet.
When to add fruit/juice? that's entirely up to you. Some like to add it in secondary for more fruit flavour, some like to add it to primary to get a more wine-like flavour; I like to do both for great flavour on both sides & added depth of flavour. It's a little more work that way, but IMHO, it's worth the effort.
Here's a link to the mead recipe section, there are a couple of blueberry recipes there:
https://www.homebrewtalk.com/f80/
Also, You might want to pick up a copy of
The Compleat Meadmaker by Ken Schramm
http://www.amazon.com/dp/B003C31OI4/?tag=skimlinks_replacement-20
It really is helpful & will explain a lot of things about meadmaking, even things you haven't thought to ask yet; I have a copy on my shelf & I use it quite a bit.
Hope this info helps.
Regards, GF.