Acrylic sign leds for bases - cut, solder, what?

I am going to try to make some acrylic signs and I am looking for sources for leds for bases -Then once you get them, do you cut them to length? and after you cut them, do you solder them or what?
I got out of electronics when the vacuum tubes went out?

There are specific points where you can cut the strips. It is also imperative to keep the polarity correct