In the top menu, select the Clients tab and then click on Add Client on the right.

Client - Add a New Client
In the form, fill in the client name and save.
Client add form

Client add form
Learn more about the option to set hourly rates in the Setting Default Client Rates section.
In our example, we created the following clients:
The view of our clients list currently looks like this:

List of Clients
Activating / Deactivating an Activity
If we no longer want to use a particular activity, we can deactivate it. Deactivated activities will no longer appear when creating budgets (they will only be visible in report filters for accessing historical data).
Activating / Deactivating a Client
If we no longer want to use a particular client, we can deactivate them. Deactivated clients will no longer appear when creating projects and will only be visible in report filters for accessing historical data.