Hello there, new to the forum so hi

I'm building a bike, first time iv done it. Converting a very old raleigh espirit, and I'm stuck with taking off out the bottom bracket. Got the chain ring off and that crank arm.

The other crank arm and bottom bracket is where I'm stuck. I've unscrewed that ring next to the crank arm and then I expected it just to slot out. It looks like its sealed on the chainring side on the bottom bracket. I need to know if this is threaded, and how do I get it out? And if it doesn't come out, is replacing the bottom bracket possible?

Sorry if this makes no sense at all haha. Thanks in advance.