How do share my login details with my Business partner so he can have full access

Hello Dcoupar, 

Welcome to the community page, 

If you have an essential or plus account with Quickbooks you can add your business partner as a company admin in the manage user section which is cogwheeel>manage users>add user top right>select company admin>next>fill in the details>save. 

This will then send them an email to accept the invite then they would create there on password and log in with the password and email address. 

If you have the self-employed or simplestart account then if they need to access the account it would be a case of the business partner logging into the account with your details.