I have had a tent donated to our agency. Where can I get directions for erecting and finding missing parts?

That is huge, it is like a house!

https://www.google.com/search?q=Northwest+Territory+Olympic+Cottage+Tent

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Wow! That is not a new model. :-) All I can suggest is that you look for YouTube videos of setting up tents, or lay it out with a couple of friends who have a lot of experience with different tents and give it a try.

This is a dog-gone big tent, even if the erected size works out to only something like 8x12 (leaving aside the screen porch) that will easily fit 4 cots 2x7 ft each. You are more likely to have problems finding tent sites large enough (flat) to allow it to be set up properly.

I don't know what kind of tent you have but there are many videos on youtube.
erecting tent YouTube

building tent YouTube

making tent YouTube

Pop-up tents are self-erecting tents that can be set up in under 2 minutes.

If it is like mine (year, etc) you simply first lay out the ground cloth (if you have one) long-wise, then lay the tent body on top of the ground cloth. Next, stake out both ends of the tent (at head and feet of tent). Now put your poll sets together (the large one is for near the head of the tent, the short for the near foot of the tent). Go ahead and put the polls in the aligned grommets (matching the ground cloth grommets with the tent-body grommets). Once you have the two polls inserted, then clip your tent to them. Now, with your tent erect, Place your fly on top and drape over the tent accordingly; then fasten the fly to the tent using the belt-type nylon clips to do so. In this case the fly does not need to be "staked", rather "belt-clipped" together instead. That's it, your're done. Don't be alarmed if your tent floor seems as though it's lifting off the ground in some areas, this is normal. Just go ahead and put your bed role in the tent and prepare your area as normal.

Free online instructions:

https://www.manualslib.com/manual/1185642/Oztrail-Villa-Dome.html?page=4

take it back to the store if you bought it as a new item
if it has been opened and was not sold as damaged stock at a reduced price it is a fair bet that there will be parts missing from it that some one else needed for a tent they had
if it was sold as not new , then open it up somewhere before you go and learn how to set ti up
for starters always lay the floor our and pin it down with the pegs supplied then put the bars through the loops first then fit the legs ( uprights) into the bars
normally the uprights on the right are anchored on the left and the reverse for the left so that the bars form a X at the sides of the tent
the center bar will have vertical up rights standing straight up
( here is a clue --- when you have worked out the positions of all of the bars get different colored electrical tape and wrap the same color around adjoining pieces so when the time comes ---red to red , blue to blue etc