The slider can hold up to 6 comps, if you want to add more on there it will be charged as extra development work but we don't recommend having more comps on the slider as it might slow the site down.
On the backend, if you click on 'competitions', you will see some stars next to each competition, this is how you'd choose which comps you want on the slider.
You can click the stars as many as you want but it will only choose the 6 you have chosen first.
The slider is also not in the order you choose it in, it's in the order of the competitions ending soonest.