Ok, so learning as I go to correct everything. My friend and I . Been playing trying to figure out the manual and fixed go system. If that could be explain a bit more. 

I believe fixed is the way the website give you go. Based on increasing your level. While using hit die add to your go. As in you roll every level to determine your go at that level. That my assumption. Only been playing for a bit now. They saying each Tim you level up you roll and add that roll to you previous one. As in adding more points at you level. 

just want to understand best I can to be a good dm as well explain to them how it works 

So, at 1st level every character gets the maximum value of their Hit Die for HP (Wizards get 6, Barbarians get 12, etc.). Then, at level up, a character can either gain the fixed amount listed for the class they took a level in, or they can roll 1 Hit Die for that class and add what they roll. And finally the total HP is increased by a character's CON mod multiplied by their total levels, so at level 2 with a +2 mod you'd be getting a total of 4 HP from the score, and at 4th you'd have 8 if you left your CON at +2 or 12 if you increased your CON so the mod was +3.

Generally speaking, if you're a new DM with new players, it's better to take the fixed amount so no one gets a few bad rolls dragging their HP down. Technically the system assumes you're committing to one path or the other for HP gained with levels, but personally I like the idea choosing between either option at level up (on average rolling should give about the same HP as taking the fixed score, but it adds a little more variation to play and if you roll low a time or two you can then take fixed a bit to bring yourself close to average again).

Thank you for this information, helps explain their hp and what. Cause each time they leveled up they talk about how their hp looks. Which is why they decided to roll for it. They way they were adding the hp seem off to me. 

Can yiy explain the hit die and how it works every level. I just assumed they roll at every level. That’s their hp for their level. They’re saying, that each time they level, they add it to what they already hap. I told them I’ll look into it, because to me that seems like huge leaps of hp increase. 

Hit points are cumulative as you level up. If you have 10 hit points at level 1, and you roll a 6 at level 2, then you have 16 hit points, not 6.

It doesn't really represent a huge power discrepancy because as the players level up, so do the challenges they face. The game is balanced in such a way that later enemies will be doing upwards of 20 damage on a hit, so player hit points *have* to keep up with that in order for the game to function. 

A worked example for a Rogue (with a d8 Hit Die with +2 Con.

Level 1: You get max roll for your Hit Die and add your Con to get your Max HP, 8+2=10.

Level 2: You get to choose, either the average of your Hit Die rounded up (5 for a d8) or just rolling your Hit Die, add your Con, then add that to your previous Max HP. So if you roll a 7, it's 10+7+2=19.

And so forth. You take your previous Max HP, add either the average roll or an actual roll of your Hit Die and then add you Con. The only exception is for L1, where you just take the maximum roll instead of rolling or average.

It's also worth noting that if you increase your Con, you get "backdated" HP too.

So say our Rogue gets to L4. At level 3 they had 25 Max HP. You take your ASI and improve your Con. You get 25 (your level e Max HP) + 5 (we're taking the average roll this time, which is 5) +3 (your new Con modifier) + 3 (your backdated HP from increasing your Con) = 36.

For the next level you just add the +3 as usual. The idea is you're not punished for increasing your Con later on.

Hope that helps.

Yes this helps a ton, thank you. I think we will be going back and fixing character sheets on go. Due to how messy it’s gotten. Just to make sure everyone gotten the correct heath they should have.