Dual suction port to pump

Hello,

I have a Bestway above ground pool that is a 20x48. I purchased the 19" Pureline Sand filter from you last summer. My pool has dual suction ports and a single port putting water back to the pool. I was wondering if I capped off one port and only used 1 suction port with a skimmer that hangs on the rail, will my filter system get enough water? I’m not exactly sure what the purpose of the dual suction even is. I have converted the port outside of the pool to go from 1.25 to 1.5 so the white Intex hose connects straight to my pump. I have it hooked up like this but I’m scared to death to turn the pump on in fear of causing damage. Any advice would help.

Thank you,