I teach at a state university. I am a permanent resident. At this moment I know very little about doing tax. What will be the steps?
If you only had income and paid taxes in the US in 2107, you can simply get tax preparation software like TaxAct, TurboTax, HRBlock, etc. These programs will walk you through the process step by step and even file electronically.
If you had income and/or paid tax in more than one country, things are more complicated. If you don't feel like reading up on how this works, I would get help from an professional tax preparer. This will cost a few hundred dollars but it saves a lot of time and head ache.
If you use a preparer, make sure you read reviews and find a good one. I once tried this in an HR Block walk in tax office. Fortunately, I had done some homework upfront, and it became quickly clear that preparer in the office had no clue how this works. After calling him out on this, he actually admitted to that.
Did you become a permanent resident of the US in 2017? Because if you became a permanent resident prior to 1/1/2017, then you needed to have filed a tax return for years prior to 2017 also. In any case, you need to gather up information about all your income-producing assets worldwide and declare all that income on your US tax return(s). It doesn't matter diddlysquat if that income has already been taxed by a foreign government (including tax deducted at source and sent directly to the foreign revenue authority); your entire worldwide income must be declared on the US tax return, and taxes paid on it. You can choose to get a tax credit for taxes paid to a foreign government, and this will reduces the US income tax that you have to pay.
Furthermore, you have to declare the existence of foreign assets to the US government, to the IRS on Schedule B of your US income tax return and separately to the US Treasury on Form FinCen 114 in accordance with FBAR regulations. In both cases, if the foreign assets total less than $10,000 at all times during the year, then the taxpayer is instructed to answer No on Schedule B to the question "Do you have foreign assets?" and need not file FinCen 114. But assets smaller than $10K does not remove the obligation to declare the income from those assets on your US tax return and to pay tax on them. Be aware that violating FBAR regulations leads to severe financial penalties when the US government catches up, so don't blow these obligations off as inapplicable to you, or think that "they will never find out about my millions stashed away in the old country".