Excel offers multiple ways to accomplish most goals, including navigation. Except for typing in a cell, a mouse can get you almost anywhere; however, power-users tend to prefer keyboard shortcuts (described here), which take practice but lead to faster performance by keeping your hands where the typing happens.
Select a single cell:
Select multiple cells:
Change worksheets:
Add content to a cell by selecting the cell then typing. When you finish, commit your changes:
Typing on the cell overwrites anything that had been entered there before.
Edit the content already in the cell:
Cells are individual boxes in a spreadsheet. Identify a given cell by its column letter and row number (e.g.: C3).
Worksheets appear as tabs in an Excel file. Identify a cell within another worksheet by adding the worksheet name and exclamation mark before the cell identifier (e.g.: Sheet1!C3)
Workbooks are individual Excel files. Identify another workbook by adding the file path and file name (in brackets) before the worksheet and cell identifiers (e.g.: 'C:\Temp\[Book1.xlsx]Sheet1'!C3).
The Menu Ribbon sitting along the top of Excel's interface grants access to many sophisticated software capabilities.