A: You don’t. That is why they are the administrator and you are not! In any organization I support, attempting such action would be considered a breach of computer policy, with termination as the likely result.
If the user enables private browsing mode on their browser, there will be no browsing history on the computer. However, this doesn’t stop browsing history from being recorded by the office router. This cannot be bypassed. The Internet Service Provider will maintain a browsing log. This can be bypassed by using Virtual Private Network (VPN). The DNS provider will also maintain a log. This can be bypassed by switching to a DNS provider that does not maintain logs.
Keep in mind that using VPN or switching DNS provider is very easy for the administrator to spot.