Bielik, who is capable of playing as a centre-back or defensive midfielder, joined the Gunners from Legia Warsaw in 2015. He has only played twice for the first team, but has Championship experience after a loan spell at Birmingham during the 2016/17 campaign.
"I want to show everyone that I can play football," the young Pole told CAFC.co.uk.
"It's a good opportunity for me to play here because I know people are going to watch me and I'm under pressure. That's what I like, I want to do my best."
Addicks manager Lee Bowyer said: "He is someone that can protect the back four. He's good on the ball, strong and he's someone that can fill in at centre-half as well.
"He's a bit like [Ezri Konsa], he can comfortably play in both positions. He's obviously good on the ball, you don't play for Arsenal unless you can play, so I know he's going to be another great addition to the squad," the 41-year-old added.
"I couldn't tell you how many phone calls [Head of Recruitment] Steve Gallen made to Arsenal to try and get this one over the line. It's been going on for a while now, so we're delighted to get him here.
"Obviously, there were other clubs involved trying to get him, like all the others that we're trying to bring in so he's no exception but that's what happens when you are trying to bring in good players."