Choose your campaign type

Make sure to come up with a map of the world or choose an already-made one, then drag hexes on the map to represent how large each area is (i.e., 150 miles). This will also be your combat map.
Some of the basic ideas behind a campaign are:
-The world is not limited to one map but rather can have multiple maps with different terrains and monsters.
-Each hex on the world map represents a certain area, usually in miles.
-Each player starts the campaign at home (a common location), moves through towns, dungeons, and other areas to complete quests or adventures that lead them across the world.
-The campaign can be as long or short as you like.
-You can build a world map by dividing your hex map into different terrains such as forest, swamp, desert and plain.
-Planning a structure for the town is essential to the game play and fun of the campaign

Create your characters

You may use the basic D&D character creation rules, or you can apply any elements from other games (they should have a certain number of hit points, initiative, etc.). Here’s an example of how I made a few characters.
Four to six should be enough for a one-shot game. I made two swordsmen and two archers, with an elf and a dwarf as the races (plus I have an extra so I can play too). The first three are classed as “fighter”, while the last two are called “rogues”.
I rolled 4d6 (with 6 being the maximum) for each ability score, except Constitution which gets 3d6 + 3. The other ability scores were all equal to the highest ability score on the dice roll. My ability scores are as follows:
STR: 12 CON: 14 DEX: 15 INT: 6 WIS: 9 CHA: 14

Pick a setting

Once you have your characters, choose a setting for the campaign. You can pick from any D&D settings (such as Forgotten Realms, Eberron, etc.) or come up with your own. You can also create a homebrew setting (see below). Whatever you choose, it’s good to name your setting (i.e., “The Forgotten Realms”, “Aldern Valley”, etc.).
This is your campaign. It’s going to feel like home to the players, and they will want to play there all the way to the end. Your setting is the character that they live in and play, so you’ll want to make it as good as possible. The name of your setting can be used on a map or in write-ups for any NPCs or magic items or what-have-you, so make sure that it’s clear enough that anyone who needs to know will know (e.g. “The Forgotten Realms” is a lot clearer than “The Realms”).

Start playing!

The DM (Dungeon Master) controls the NPCs, monsters, and other events that affect the players. The players’ actions, combat statistics, and dialog with NPCs are all determined by the DM. The DM can also create their own NPCs using D&D Beyond rules or come up with their own. The DM creates the characters (player and NPC) and then starts the campaign with a pre-generated adventure. This article provides information on how to set up, run, and play a campaign in D&D Beyond.