Hi

Actually it's better late than never but the best thing is you are not late at all for SBI PO preparation
Minimum age required to be eligible for SBI PO is 21 years and you are only 20, so you are not at all dear

Now , if you feel like you are  very weak to prepare for SBI PO then let me tell you that there are lots of people who are average at studies but they work hard and clear even the most competitive examination like UPSC , so if you work hard and prepare will then you can definitely crack SBI PO
Also,
there are many people who qualify SBI PO etc bank exams in their 1st attempt and that also in just 1 year preparation or even less, so even if you are starting from scratch and you want to prepare in 2 years then you have plenty of time to prepare ,

Follow the below tips to prepare :-

First of all go through SBI PO syllabus and its exam pattern

Go through the previous years’ question papers and see the level of difficulty of the question paper so that you can prepare accordingly

You can take help of video tutorials available free on platforms like YouTube as well

Go through newspaper daily for General Knowledge and current affairs

Once you are done with syllabus go through mock test and identify weak areas and work on them

Thank you