The builder has different sections corresponding to different parts of the creation process.
The home screen allows you to change your character level, set a portrait and name, and set some character preferences. You can skip the character level or name/ portrait at the start (they'll be available in other sections too). Note that the default advancement method is Milestone, but you can change this to XP if that's what your campaign uses. Fixed hit points are also the default, but you can adjust that in preferences as well.
Choose your race here. Remember that only races from the Basic Rules/ SRD/ EEPC are available during the beta.
No firbolgs yet!
Choose your class here. Remember that only classes and subclasses from the Basic Rules/ SRD/ EEPC are available during the beta.
No swashbucklers yet!
Determine your ability scores in this section by using the standard array, point buy system, or entering them manually.
You can choose your portrait and set your character's name here, as well as select your character's background. Notes of all sorts are available to flesh out more details for your character.
This section is the starting point for what will eventually become a more feature-rich inventory management system. Our goal for initial release is to allow players to record, equip, and use equipment at least as well as you can with pen and paper. On top of that, any equipment that affects your character's statistics (such as armor), will automatically update the character sheet with those modifiers. You can also track attuned magic items here.
Again, a full-blown inventory management system is definitely on the roadmap for this year - things like party inventory, trading/ selling, and more.
This final section provides helpful context and links to go and play your character, including going to the digital sheet, exporting for print (which will be available later in the beta), and creating or joining a campaign.