To use web analytics for SEM, you need to define your goals and objectives for your campaigns, choose the right web analytics tools, integrate them with your SEM platforms, collect and analyze data regularly, implement and test changes based on the data, and evaluate and report your results. Firstly, consider what you want to achieve and how you will measure it. Then select the tools that suit your needs and budget – Google Analytics, Adobe Analytics, Moz, SEMrush, etc. Afterwards, ensure the tools are integrated with your SEM platforms such as Google Ads, Bing Ads, Facebook Ads. After that, collect and analyze the data for patterns, trends and anomalies that will help inform decisions and actions. Finally, test changes on variables such as keywords, bids, ad copy or landing page design before evaluating the results.