First, both of you should read the free Basic Rules for D&D, or read the Player's Handbook. I prefer the Basic Rules for newbies, because a lot of it is condensed without any added fluff to distract you. If you've done that, then you are ready to create a character and try your first game. The Starter Set box is really great for 5E. If you are DM'ing, I would say watch some podcasts specifically for that adventure (Lost Mine of Phandelver), and see how other DMs handle the intro and combat parts. Be sure to look up any rules you have questions about. The DM has a more difficult job than the player, so if you are new, and a DM, you're going to be pretty busy. Players have it easy, they just have to focus on their character, and know their spells and special rules for their race and class. It will be slow going at first, especially for spell casters, but it gets easier with practice (like anything). There are a few things that can help out spellcasters, like spell cards, or printouts with spell summaries you can make yourself. But don't hesitate to ask your player(s) to read up on their character abilities and know them...it's the least they could do if you are busy with DM'ing. If you get that far and still have questions, you can ask around. These boards aren't really for general DM help, but more for Roll20 related stuff. You should try places like Giants in the Playground Forum, Wizards D&D Community Forum, or EN World Forum. Those are the big 3 for most D&D related help IMO. Just Google them.
