hello gaurav verma,

so you're going to prepare for the jee mains.i hope you're gonna prepare for april 2019 jee mains not for jan 2019,since you're having very few days for january exam. 

whatever the exam is,first you've to know syllabus and exam pattern to know jee mains syllabus please refer this link:

https://engineering.careers360.com/exams/jee-main

after that you've make a plan/schedule to whole syllabus/important topics (it's depends on your capability) to know important topics,

https://engineering.careers360.com/articles/jee-main-2019

prepare ncert text books and exemplers.try to solve more on your own.

all the best!

note:if any links available copy and paste it in the address bar of your browser.

I Hope this information will be useful to you.

if you need additional information,let us know to help you.

Thank you!!!:)