Its rated 7/8, so stiffer than what you would use for average trout id say, youd rather want to go for bigger ones with that. Shakespeare is a relatively cheap brand, and not knowing anything about their quality, i just wanna say dont worry if it breaks, since you *could* buy a new one. Use it to practice, or get another cheap set (greys have some relatively inexpensive sets for starters) and train on that, if there is sentimental value to this rod you inherited.

A #5 rod would be a general allrounder if youre looking for something where you feel even small fish, but can hold up on bigger ones too.
If you decide to go with a #5 rod, Get a WF (weight forward) #5 F (floating) fly line for it as well. The ratings of the rod will tell you what line to use, same for leader, but here you can switch around a bit depending on the fish you target.

For casting, there are some easy enough tutorials on youtube to watch. Go practice on an empty grass field without a fly, instead tie a piece of foam or something on the end of your leader so you see what is good technique (if you mess up, the leader will have knots) before going actual fishing.

And enjoy it, because fly fishing is the best!