Hi,
To receive an OAuth access token of an advertiser, the most common way is that the advertiser would have to login with their credentials and grant you access as described on https://dev.twitter.com/ads/overview/obtaining-ads-account-access
If your account is given Ads Manager access, you use your own access token instead of the advertiser token.
If you are talking about regenerating the OAuth token, this may be done by revoking and re-authing. There is no other way to carry multiple OAuth tokens to a single Ads Account (this would defeat the purpose of our rate limiting mechanisms).
Thanks,
John