One question,
If i want to add a new theme, how do install it on my Fascinate?
Also if i want a new ROM must I also instal a new kernel?
I downlowded SDK kernel last night.
Forgive the newbie questions. I am just trying to learn all I can.
First off, that's 2 questions.
You'll need to have CWM Recovery flashed to your phone if you haven't already. Follow the sticky for it to get the files you need (CWMRecovery.tar.md5 and update.zip) and instructions on flashing it.
If you are using ROM Manager to get themes, select the one you want in the Download section and when it's done you will get a popup with check boxes to backup your current ROM and wipe cache/data. Neither one are necessary for themes so you can leave them unchecked and just hit OK. It will pop up another window for you to confirm the reboot into recovery mode to install it. Just select OK and the phone will do the rest. When it comes back up, your new theme should be applied. If you're downloading a .zip file of the theme you want, you need to copy it to your SD card and install it with CWM Recovery manually. To do this, you'd boot into recovery mode by powering your phone on by holding volume up + down + power until you see the Samsung logo, then, navigating with the volume keys and selecting with home, choose apply update.zip to get to CWM Recovery, and navigate the same way, but select with the power button to install .zip from SD card, and navigate to where you put the .zip file of the theme. I'd recommend making a backup in CWM Recovery before flashing any theme so you have a stock theme point to go back to. Especially if you plan on trying different ones out as sometimes they'll cross if one theme doesn't change what another did, you can end up with icons from multiple themes.
As far as the kernel goes with a ROM, you don't HAVE to flash one as long as the update versions match (which they probably will these days with no ROMs of leaked updates currently). For example, before we got the latest Verizon update for version DL09, the official phone version was DI01. Some developers had made ROMs based on Verizon's unreleased, but leaked update, DJ05. Thus when installing them, you needed a DJ05 kernel to match it as your DI01 one would not work fully. Today, you probably already have DL09 and would be looking at DL09 ROMs so this isn't an issue and DJ05 and DL09 ROMS and kernels work together. So you can keep the stock kernel with any current ROM, or even use a different kernel with a stock ROM like I do. Kernels handle the hardware/software relationship so they're more responsible for performance. You would notice greater differences flashing a kernel over a ROM, or you can do both. It's all up to you!