When another person in my firm emailed me a 2019 data file, it was in read only mode. How do I enable being able to input and change data?

[Just-Lisa-Now-]

From Windows file explorer, find the file where you saved it and Right click on the file and choose Properties...is the read only box checked?  If so, uncheck it and see if that solves the issue...if that box isnt checked, then something may have happened to the file, ask your colleague to resend the file.