Make Excel Sheet Non-Editable with Guidance for Future Use

I need help making an Excel sheet non-editable. The file has extra cells/boxes that need to be cleaned up, and I want the main sheet to be view-only while allowing specific edits in designated areas. Additionally, I’d like step-by-step guidance on how to replicate this process myself in the future. This is a quick task and needs to be completed ASAP. Note: No data input is required, just better formatting so it can be shared easily without issues (e.g., when converting to PDF).