Welcome to the forum!
You most definitely can use that soundbar as a center speaker. If I'm interpreting the pictures and the owners manual correctly, that soundbar is essentially three speakers within a single cabinet. So, you can connect each speaker separately and still have it work. If you have one set of speaker outputs for the center channel (for example, on a typical A/V receiver), then you'll want to only connect to the center set of speaker terminal on the soundbar. You don't want to split speaker-level connections to the three sets of connectors on that soundbar.
However, if you are going to use an external amp (or amps) and you have three power channels that you can devote to the center speaker, then you could split the center speaker pre-amp output from your receiver (or processor) into three inputs to the amp, then run three speaker-level connections to the soundbar.
Does that make sense? In a nutshell, you can easily connect just the center speaker connections on the soundbar. If you want to use all three connections, then you'll want three amplified channels to run each separately.
