You can edit the name you initially gave to a campaign by taking the following steps:
Step 1: Access your campaigns library by clicking Campaigns from the options on the left panel of your account.

Step 2: Locate and click on the three dots at the extreme right of the campaign you want to edit.

Step 3: Select Edit from the pop-up options.

Step 4: Change the name by clicking the box, then click the Edit option below after editing it.

The campaign should now show the new name you just gave to it.