This BSc thesis presents the process of planning and developing of a web application, used to support advertisers that use Facebook advertising platform, which is one of the biggest such platforms, with the main focus on the frontend of the application, it's user interface and user experience. The application's frontend is mostly written in ReactJS, and it uses GraphQL to query backend. The application automizes the onboarding process of new clients and lets them digitally sign the contract, that can be in multiple languages, that is needed to start advertising through the application. The clients can also add money for their advertising needs through the application. The application also has a separate segment for administrators, where they can quickly look over the clients, their contracts, statistics of their advertising accounts, generate statistic reports for the needs of finance, managing entities used for advertising and setting spend limits for those entities.