I had (have) an account Username: Stan_Counsell. I had difficulty operating that account since I may not have had administration rights (although it had been my intention to do so. I opened a new account with the username oak_tree and now have difficulty accessing that account. I feel there may be a conflict between the two and since the latter is the one that I progressed furthest I need to close my earlier account.
There's not much to go on here. You haven't told us the version of Moodle and you haven't told us what problems you are having.
To delete a user, go to Site administration > Users > Accounts > Browse list of users
Find the user and click delete. Obviously you need to be an administrator. But, somebody needs to be administrator!