SOAP Service Authentication

I am developing HTML web resource  which has some search function. The problem is that sales should search through Accounts and Leads but they can see only theirs so the search is not working like it should.

I am using SOAP services for that functionality andGenerateAuthenticationHeader(); which generate something like this:

<soap:Header>

 <CrmAuthenticationTokenxmlns=“http://schemas.microsoft.com/crm/2007/WebServices“>

   <AuthenticationTypexmlns=“http://schemas.microsoft.com/crm/2007/CoreTypes“>

     0

   </AuthenticationType>

   <OrganizationNamexmlns=“http://schemas.microsoft.com/crm/2007/CoreTypes“>

     AdventureWorksCycle

   </OrganizationName>

   <CallerIdxmlns=“http://schemas.microsoft.com/crm/2007/CoreTypes“>

     00000000-0000-0000-0000-000000000000

   </CallerId>

 </CrmAuthenticationToken>

</soap:Header>

How can i authenticate as admin so the search see all Leads and Accounts?