How depreciation expense and depreciation charge are defined for assets
Different tax jurisdictions use different rules.
The most common rule is to charge the cost of the asset over the lifetime equally year by year
So if the asset cost 10,000 and has a 10 year lifetime, then the depreciation charge is 1,000 per year for 10 years
Other options are a reducing balance - for example 25% of the balance each year so 2,500 in year 1, 1,875 in year 2, 1,406 in year 3, etc
If you are asking how do you enter depreciation charge in Manager. the guide https://www.manager.io/guides/9119 explains it in detail