If you're going to be contributing a lot of material, you should create an account. You don't have to, but there are lots of benefits. Making an account makes it much easier to communicate with other contributors, and to follow certain rules (described below).

Do not make an account for your group, organization, or company. User accounts must represent individuals. You can, however, include your organization's name in your username. So, for example, XYZ Association is not an acceptable username, but J. Doe at XYZ Association is fine. But you don't have to include your organization's name: J. Doe is fine, too.

Paid contributions to Wikipedia

If you are being paid for contributing to Wikipedia (for example, as part of a job in marketing or public relations), you must disclose this as part of the Terms of Use. This means you have to say that you are being paid and who is paying you. The easiest way to do this is by making a note on your user page (the link only works if you have an account and are logged in). If you don't have an account, there are other ways to make this disclosure, which are described in the Terms of Use.

More information is available in the FAQ on this requirement.

The next step depends on your answer to this question: Does the subject you want to write about already have an article on Wikipedia?