Assuming the "arc fuel" is a variety of "ingot" the same way Uranium Ingots power regular Reactors, you'll want to designare an ingots inventory panel ("Panel [TIM Ingot]"), make sure you have at least one "arc fuel" on hand, and take a look at that panel. TIM should find the fuel item and list it there, which will tell you the "internal" name for the "arc fuel" item (probably something like "ArcFuel" or "ArcReactor_Fuel" or similar). Once you know that name, you can use it to tag your Arc Reactors, but you might have to also use the FORCE: tag to make TIM override what it thinks it knows about the items that are allowed to go into reactor-type blocks. So, for example, "Arc Reactor [TIM FORCE:Ingot/ArcFuel:10]".

I think the issue is, ARC fuel is set to a Component. it sorts that way with TIM.. I am going to try the "force" command to have TIM force the fuel into the reactor. Someone states this in another post. the reactor is set to "Fuel" but the actual Fuel is set to Component. and TIM won't place it in.

Kemik makes sense, IMHO the mod author used the wrong item type. They should have used the ingot type for the fuel but instead used the component type. That's unfortunate. You'll need to do as you say and FORCE the correct item.

Would be pretty cool if you find the time to update Tim so it can handle Nanite Mod too. At the moment tim doesnt recognize the nanite factory at all.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=655922051
Or is there a way i can help tim to handle it already?

I play with the nanite mod all the time. There are two ways to handle it. First, do nothing, the nanite factory will pull the components it needs from your cargo system as needed.

Or you can treat the nanite block as if it were a cargo and tag it with something like [TIM Component:200] (puts 200 of each thing in the blocks inventory).

Either way has worked for me, but I prefere the simple route and I rarely tag the nanite block. Instead I usually have a button panel for ease of turning on and off the nanites as required.