Before you can request credit for a client, you need to ensure you have setup your Credit Controllers. This can be done by following the steps here.
To request a credit limit, head to the clients profile that you would like to do this for and on the top right, you will see the Request Credit button, as shown below.

When you click request credit, you will see the following popup:

From the Requesting Credit Limit dropdown, you will be able to select the limit you would like to request.
The dropdown for Secondary Additional Increase is used to instruct the Credit Controller to increase the limit if possible, or to leave the existing limit in place. If your request is over £10,000.00, we will show you an area to provide some reasoning behind the request, to help expedite the process.
When the request is made, an email is sent to the lead consultant and the credit controller, where they will be able to manage the request and you will receive an email back upon the controller completing this.