post https://marketplace.walmartapis.com/v3/token
Get access token by providing Client ID and Client Secret.
An access token expires after a certain interval, so you will have to refresh a user's access token. You could use refresh token, obtained from the token API call using authorization code grant type, to get a new access token. Refresh tokens remain valid for a year.
Guide reference - authorization_code
Guide reference - refresh_token
Guide reference - client_credentials