Hi @AndyPowerAppNew,
Sounds like you want to create a login screen.
Here is the thing, to tick a Checkbox to accpet your t&cs and then make the login button visible, you just need to do the following job.
1). Set the Checkbox OnCheck property as below:
Set(Varvisble,true)
Set the Checkbox OnUncheck property as below:
Set(Varvisble,false)
2). Set the Visible property of the signin button as below:
Varvisble
3). To update your t&cs, you could add a Text Input control and you can update something there by write a Patch() function on OnSelect property of a Button:
Patch(list,LookUp(list,ID=xxx),{t&cs:TextInput.Text})