Five stages with agreed outcomes and a way of working that fits your task.
To manage a project, you need to know what is happening now, what decision is expected from you and what comes next. We organize the work around five stages: Discover, Design, Build, Launch and Run. At the start we agree on the goal, the people involved, the scope and how results will be accepted. That gives everyone a shared basis for daily decisions and changes.
In Discover we research needs and set priorities. In Design we create the structure, prototypes and visual design. In Build we develop the product and test its user flows. Launch covers preparation and go-live. In Run we keep things running and plan further development based on actual needs. What each stage includes depends on what you bring to the table.
A fixed-scope project works well for a well-defined task. For long-term development you can choose a dedicated team, and for regular changes and technical work there is monthly support. Let's talk through your situation and agree on the format that gives you the level of involvement and control you need.