That's a good price for that big tank! I can give you brief instructions now, I'm about to leave for the day, you just have to set up an account, that is usually on the left side, then you want to list a new post, that is on the right after you make an account. The tank you can put under community, then the pet section, or just the regular for sale by owner in household or the general section. Once you pick all those selections, you can make your listing title and price, then you should list the deminsions and how many gallons. The, there should be another button or page to attach the picture. Does this all make since? Lol. If no on helps before tonight, I can do it for you