[RPG] Am I supposed to add the Attack Roll Bonus to the Attack Roll along with the Ability Modifier and Proficiency Bonus

Those numbers are your overall modifier for that skill or saving throw. They include your proficiency bonus if you are proficient in them, otherwise they are just your ability modifier for that skill or saving throw. They're pre-calculated and listed on the sheet for convenience during the game so that you don't have to add up all your modifiers and Proficiency bonus every time that roll is made.

So if your example Cleric is proficient in Wisdom saving throws and has a Wisdom score of 15, their Wisdom saving throw modifier = proficiency bonus (+2) + Wisdom modifier (+2) = +4, which is the number that will be listed under Wisdom saving throws.

On the other hand, your Cleric probably doesn't have proficiency with Dexterity saving throws, and let's say their Dexterity score is 8. Their Dexterity saving throw modifier = no proficiency bonus (+0) + Dexterity modifier (-1) = -1.

There are other factors that can affect this calculation, such as the Rogue's Expertise feature, but this is the basic calculation that will be used in the vast majority of cases.

Whenever a PC makes what 5e calls an Ability Check, such as Dexterity(Stealth), they roll a d20, add their Ability Score Modifier, and their Proficiency Bonus if they are proficient with that skill. A PC Proficient in Stealth would add their Dexterity Modifier as well as their Proficiency Bonus.

This information is in Chapter 7: Using Ability Scores. It starts on p. 173 of the PHB(or p. 57-59 in the Basic Player Rules), and describes how a PC's Ability Scores come into play during the game, namely Ability Checks, Attack Rolls, and Saving Throws. The Chapter details some of the things you can do with the Ability Checks as well.