The whole income tax is divided into chapters.
or in easy way the whole income tax is divided into different heads.
For e.g:
Salary : Section 15 To 17
House property: Section 18 to 27
Business: Section 28 to 44 etc.
First try to learn which section belongs to which head.
Then section in gross , means how sections are interlinked to each other.
For e.g.
In salary: Section 15 defines about what is salary, what is employer employee etc.
Section 16 describes about deduction
Section 17 tells about what salary includes.
After learning sections, its interlinkage , after that start linking it to other sections.
Moreover, the most important thing which require to gain this: Is
Your interest to learn
Patience
Daily practice
Last but not the list (your way to learn)