Hey guys, i'm not sure if this is the right section, but i've looked everywhere and this seems to be where questions are asked.

Alright, So i want to get into textures and designing them, I've learnt the basics of photoshop but there's one thing that i really cant figure out.

I open up my sheet on 128x128 and to keep it simple, i mark the middle with the rectangular marquee tool, I do my design and then i copy it, Then move the marquee to the other side of the page, And paste the half picture onto the other side, and then i flip it, They go together nicely.

After that, i can only edit one side of my design. I'm very new to photoshop and it's really getting on my nerves. I understand about the layers, but i dont see any way to get around it. Can someone help me please?

PS: I may seem like a dumbass to some of you guys, but you've got to start somewhere, right? Hopefully i'll be spitting out some great designs, but i just need to sort this problem out.

Thanks.