Setup Your Email Accounts
Your new hosting service will have some sort of control panel that lets you set up your email accounts. There are usually just a few parts to this:
Of those, not all control panels allow you to specify the quota, although it is very common to permit it.
What Usernames Do I Use?
This is really the tough question. I recommend that everyone who controls their own domain have several eddresses of their own.
The bottom line with email right now is that spammers are everywhere--and if you want a permanent email address, you need to make sure that you keep it from getting on spam lists.
To do this, have one eddress which you give only to personal friends (yes, that includes family). Don't use it when you fill out web forms that require your address, don't give it to businesses, don't give it to anyone who might sell or mass distribute eddresses. (Your first name works well for this one.) And whatever you do, don't put it on a web page!
Then, create at least one other username that you can use when you need to provide an eddress to a business or a web form.
I say "at least one other", but I actually recommend that you have several. That might sound like overkill--an acquaintance of mine recently said that I had so many eddresses that he was thinking of starting to call me "Sybil". But it really helps me compartmentalize my email and limit the spam I receive.
So, here are some additional ideas for usernames to use: