I am presuming you already know how to get to the Chrome menu button and to select Settings from said menu. [If not, just say so.]
Once Settings open search on "On Startup" which is a section with three radio buttons (and you'll be selecting number three):
Once you select that radio button several things appear depending on what you've done in the past:
Obviously, if you choose the "Add a new page" link you get a pop-up dialog asking you to enter the URL for same. You can enter more than one page by activating this link repeatedly if you want multiple tabs to open when Chrome starts, each with one of the specified webpages.
Any additional questions please ask.
Brian - Windows 10 Home, 64-Bit, Version 1809, Build 17763
Explanations exist; they have existed for all time; there is always a well-known solution to every human problem — neat, plausible, and wrong.
~ H.L. Mencken, AKA The Sage of Baltimore