OK--you're enthusiasm is going to carry you...which is good. Please know simply purchasing a sophisticated camera and lens does immediately guarantee SPORTS ILLUSTRATED quality shots. Many of us on this site have spent years developing our skills (pun intended for those of us who learned in the days of film, darkrooms, and manual focus lenses.) That said, you have a number of factors in your favor.
First, your grandson plays a position that should give you plenty of opportunities to shoot him exclusively in action, especially since you are in the stands. If at all possible try to get as close to the field as you can. Since your shooting in daylight, also try to sit with the sun either behind you, or to either side; otherwise you will be shooting into the sun and your subjects will be mostly silhouetted. With the crop factor on your camera your lens will reach fairly far onto the field.
Those are the easier parts of my advice. My only experience with Canon cameras was back in the 80's with a AE-1p--a film camera. So, the basics. As long as you have sunlight, I would suggest setting your ISO at 800. You should set your shutter speed at 1000. Then your aperture setting should be automatic. Since you have at least a week before the next game the following link should be elementary enough to help you understand the settings I just suggested. It features your camera.
https://www.tomsguide.com/us/canon-t6-user-guide,review-4590.html
If your camera allows "burst shooting"--where when you push the shutter release it fires multiple shots, you will want this setting. Make sure your battery is fully charged. Don't bother using your flash--it doesn't have enough power to affect the quality of the pictures, and will waste the battery.
As your grandson lines-up for the play, train your camera with him completely in the frame, and 1/2 depress the shutter to prefocus your lens. As the play happens, stay on him, and when a pass comes his way, start firing before--before--he starts to catch it. Here's a trick, since your a newbie. Whichever eye is not in the viewfinder, leave it open and use it to give you a wide-field view of what's happening to help you anticipate the action. It's hard at first, but becomes second nature after a while.
Here's another help: When holding your camera, place your left hand underneath the lens so that your elbow rests on your abdomen. This provides a simple tripod effect, and helps steady your lens.
To suggest much more will be overkill. You should have several games left in the season to allow you plenty of opportunities. I will let you know--having worked with countless individuals on HS sidelines over the years, it's important to have an open mind as you review your shots. There are going to be a lot of duds. Just learning to incorporate light, focus, and high action are difficult. It's part of the learning curve. You have a number of challenges just from having to shoot from the stands.
But, shoot, shoot, and then shoot some more. Don't be afraid to post some on here and ask for help. Most of us will want to help you improve. Also, the internet has numerous sites dedicated to helping you. Don't hesitate to look at the other posts in this section...some such as Jules Karney are good about tagging their settings on their shots--take note, and see if these settings will work for you. The ones I gave you above are just starting points. I can't predict actual lighting, but I can get you close.
Hopefully by season's end you will have a scrapbook full of treasured shots.