Orraloon is spot-on, and you probably need supports either side of the saw too, or at least another pair of hands to help for the job you describe.
You can get cheap roller stands, and they do work (it's what I do), but for stock that long, and round too, cut close to the wanted length first so that the pieces are as short and lightweight as possible.
Two final thoughts:
1. "poles" such as fenceposts, electrical poles etc. are usually purpose grown, and made from the entire trunk of the tree. I can't remember the species, but probably a redwood of some sort, as a trade off between cost and durability. If you're cutting through a diameter, expect the pieces to want to warp and twist a fair bit, and possibly for lumps of the really soft heartwood to simply fall out as the timber settles. You are unlikely to end up with a nice finished surface you can use, even after planing. That may or may not be a problem for you.
2. Even with a thin kerf blade, you will be making the saw work hard. You'll make a lot of sawdust, and from damp softwood it will tend to clog. So you need dust extraction, and ideally a lot of suck just under the table, to keep the lower guides as clean as possible. If getting a blade from Tuffsaws, tell them what you are doing, and take their advice: it's really "resawing" and the blade needs coarse teeth and deep gullets, possibly even a skip-tooth form, so it can clear the dust easily. And get at least two, so you can carry on when one breaks - likely in this context!
If this is a one-off task, I'd consider taking your stock to a local sawmill, if they have a suitable "small" bandsaw. They are likely to be better set up to do it well, albeit probably with thicker kerf blades than you may want to use.
I'm not trying to put you off, but what you are trying to do is challenging for a first job with any hobby-sizzed bandsaw.
E.
PS: obviously, if these are squared posts, the job does get easier, but you still need dust extraction, and probably help!
