If you don’t have access to store’s admin panel, but you have access to a database, you can easily add new Magento admin panel user via MySQL script.

Before you launch the next script, please, be sure your password is 8 symbols length and has at least 1 digit.

LOCK TABLES `admin_role` WRITE , `admin_user` WRITE;
 
SET @SALT = "mr";
SET @PASS = CONCAT(MD5(CONCAT( @SALT , "password") ), CONCAT(":", @SALT ));
SELECT @EXTRA := MAX(extra) FROM admin_user WHERE extra IS NOT NULL;
 
INSERT INTO `admin_user` (firstname,lastname,email,username,password,created,lognum,reload_acl_flag,is_active,extra,rp_token_created_at) 
VALUES ('First name','Last name','email@example.com','username',@PASS,NOW(),0,0,1,@EXTRA,NOW());
 
INSERT INTO `admin_role` (parent_id,tree_level,sort_order,role_type,user_id,role_name) 
VALUES (1,2,0,'U',(SELECT user_id FROM admin_user WHERE username = 'username'),'First name');
 
UNLOCK TABLES;