Wooden shafts were the standard for many hundreds of years, and frequently fired from very heavy bows indeed... 100 pound plus "warbows".
One needs to match the spine of the arrow to the draw-weight of the bow, which should be marked prominently on the bow.
If not, any archery shop should be able to furnish a scale to determine same.
I would not go with the fellow advising you to "just go out and shoot it". Just as with most activities, there's a right way and a wrong way. Archery is a refined activity that's been done since pre-history, and there are well-established techniques for shooting that will maximize success.
Stance, draw, form, release, follow-through... All essential to good shooting.
You'll need a tab or shooting glove, an arm-guard, perhaps a new string. You want a string made for this type of bow, using old-stye B-50 Dacron which has a little "give". Modern stretch-free materials can be very hard on a traditional bow.