First you need to prepare an import file (excel/txt). Include the Campaign Id field (Eloqua's) and Campaign Type field. If you want the changes to also synch over to your CRM (e.g., Salesforce) you'll need to use the External Campaign Id (e.g., 18 digit Salesforce ID) instead of the Eloqua Campaign Id.
Go to Campaigns > Select the >> (upper right corner) > Import Campaigns
If only updating in Eloqua, use the "Add New or Update Existing Campaigns". If you are wanting the updates to also synch over to Salesforce, use the "Create/Update Campaigns and Send to CRM".
Configure the field mapping step and finish.
Thank you very much for your feedback! It took some time to see the changes but it did work, again thank you!