I have just bought a tasco 302058 telescope. As I

Many vendors do not provide a manual as such, just pages of product warnings. Your local library's science section should have several books on telescope use - although not on yours specifically. Also, see if there is a local Astronomy Club (check local schools science teachers for info); they are usually quite happy to help.

I have the original documentation from when my Dad purchased a Tasco 302058. I also have a list of accessories with part numbers that may prove helpful.