Hallo, i just started to play this game and rolled a TechPriest.

What kind of aktions can i do with TECHUSE ?

What can be done with tech-use?

hmmm... lets see, you can do alot of things. You can try anything you want with a tech item. You can try to build something from scratch to aid you in combat, but maybe a traid skill is more commonly used for this. You can try to figure out an item works. You can also repair items and things of that sort. An example in the book is trying to repair a warp engine that has been dead for thousands of years.

Alot of things are possible with the skill.

Is it for mechanical technology only ? Or are electronics and computers covered by this skill, too ?

They are.

Contrary to what RoBro said, building stuff is not covered by the skill - that's what Trade(whatever) is for. Knowing how stuff works would also likely be Common/Academic/Forbidden Lore(whatever).

Tech-Use is used to operate stuff. Any gadget that is not relatively user-friendly (and face it: The Ad Mech isn't exactly known for building stuff that way) will likely require tech-use to operate.
What is perhaps equally important: It's used to help other people operate stuff, as you can use Tech Use to aid others with any other skill as long as machinery is involved, meaning that you can for example add a +10 bonus to any Pilot check if you have access to the engine room of your vehicle.

Another vital use of tech-use is that it is tested to recharge a las gun charge pack from any machine. So as long as there is a piece of machnery near by a tech-using character need never buy ammunition again.