About rolling dice functionality

[Warfare]

How do you use dice functionality? I've tried experimenting with different checks, like Strength, Intelligence, but the bonus from the parameter ain't added at all. Do you have to add it manually? In this case, what is the point in choose which parameter to check?
Do you have to apply it manually too for checks in persuasion and thievery?

[CuznJay]

I've been unclear about this myself. I think the easiest way is to have the players make a general D20 check, and then apply a bonus yourself using something like D&D's Stat Bonus chart.

Here is a good rundown on Ability Scores & Bonuses:
https://roll20.net/compendium/dnd5e/Ability%20Scores#content