If you want to use all features which Aleeva has to offer or the server you joined wants you to add an api token, here is how you do this. As the api token is assigned to your discord account, you have to do this just once and it will work with every server which uses Aleeva.

Here is a step by step guide for adding an api token to your account:

Use the command /api-key add
Click on the button Add new Api Key or Add new Light Api Key
Open https://account.arena.net/applications and create a new key
Past the key into the dialog Aleeva shows you
If your key is valid and has all needed permission you should see a confirmation

Step 1: Add a new api key

Use the command /api-key add in any channel you like.

Click on the button Add new Api Key or Add new Light Api Key
Now you have to create a new api key for Guild Wars 2. You can do this here: https://account.arena.net/applications. Please make sure that you select all the needed permissions during creation of your key because you will not be able to change them later. The api key should have at least the following permissions: account, builds, characters, inventories, wallet, progression and unlocks. If you opt for a light api key, you api key needs at least the account permission.

You can copy the api token with the icon shown in the image

Now past the key in the dialog Aleeva shows you. She will then verify it.
If everything is perfect, Aleeva will send you this confirmation.

Step 3. You're done!

That’s it! Now you have successfully added an api key to your Aleeva account. From now on you can use all commands which require a key. Also if you are on a server on which Aleeva managers roles and/or names, you will now get the roles/name which match the conditions of your key.

Troubleshooting

Why does Aleeva need all these permissions?

Aleeva requires this set of permissions (account, builds, characters, inventories, wallet, progression and unlocks) because it allows all Aleeva commands to be usable.

If you only want to get verified on a server and do not intend to use Aleeva, you can opt for a light key, which only requires the permission account.

The full key ensures that all of Aleeva's features are available, so the bot works without issue.

The reasons why specific permissions are needed:

Account - Used for account verification with Aleeva
Builds - Allows YOU to use Aleeva functions related to builds (such as traits in PvE,PvP and WvW as well as equipment loadouts and masteries)
Characters - Allows YOU use Aleeva commands relates to specific characters (such as listing your character birthdays)
Inventories - Allows YOU to use Aleeva to search for specific items in your character inventories (e.g !!li or !!ufe command)
Wallet - Allows YOU to search for items in your in-game wallet (such as a particular map currency or festival currency, this does not relate to real world financial information about your account)
Progression - Allows YOU to use Aleeva features to query related to progress (such as what raid bosses have I killed/what achievements am I missing)
Unlocks - Allows YOU to query Aleeva about things you have unlocked in the game (such as mount skins, dyes, minis etc)
Guilds - ONLY needed by guild leaders to check the rank of members in the guild (to map roles in-game to roles in Discord)

If we allowed the users to pick and choose the API permission by themselves, it would end up that they would need to change the API token permissions multiple times to be able to use all of Aleeva's commands and features. This is not what we want for our user's experience with Aleeva. Also this would result in problems like why does one feature work and not another and so on. In addition to this the API tokens are saved globally for the user, to allow it to work across all Discord servers that the user has access to (that use Aleeva) no matter what features of Aleeva the server's use. The pvp permission is the only optional permission because we only have one pvp command so far.