-Please visit https://www.nem.io/install.html and download the Nano wallet.
-Extract the file to your desktop(or somewhere else you like) and double click on the file "start.html". -It'll open a browser in your pc and fire up Nano wallet.
-After this click on the "Signup" option in the top right hand corner.
-Choose "Simple wallet" and fill in all the details.
-Provide a Wallet name and type in a very strong password. Remember your password should be very strong and really unique. The password should contain, preferably, more than 20 characters(use special characters to make it more stronger). I prefer a password of more than 32 characters.
-Leave the last option as "Mainnet" itself.
-Then click on "Create simple wallet".
-Now your browser will download a wallet file. Visit the folder where the wallet was downloaded into. Make a copy of the file(Don't cut/paste it, just copy it) and keep it somewhere safe for backup.
After you are completed with creating the wallet. Now click on "Login" button on the top right hand corner. Select the wallet name that you just created and enter in the password. Use the address in the wallet to withdraw your XEM from Poloniex. Remember never share your private key with anybody. And welcome to NEM