@janeweinstein0,
Below is a link on changing your username.
https://www.ebay.com/help/account/changing-account-settings/changing-username?id=4198
However, before changing it, tell us if are you having problems receiving payments or making them?
You are a new seller and if your PayPal account is showing Payments marked as Pending, then that is because of PayPal's 21 day hold placed on all new sellers accounts, even those who have bought from their account. The link below explains the hold and ho to get your funds released sooner.
https://www.paypal.com/us/smarthelp/article/why-is-my-payment-on-hold-or-unavailable-faq1987
"THERE IS NO SUCH THING AS FOOLPROOF, BECAUSE FOOLS ARE SO DARNED INGENIOUS!" (unknown)