can you please help me around how to use my first tube amp?

While a visual inspection  of the inside of the amp is helpful, one sort of needs experience to spot a burnt resistor or a bulging capacitor or other visual signs of distress.  Having access to a tube tester is also nice, but decent ones are not cheap. 

I don't think testing capacitors makes much sense.  Capacitors generally can be tested only if they are removed from the circuit.  The only in-circuit test that might indicate a problem is ESR (equivalent series resistance), and this is at best a rough measure.  Also, most capacitor testing that can be found on multimeters is essentially useless because they only make measurements at very low voltages.  The proper meters are dedicated capacitor/inductor meters and these can be very expensive (common price for a used high voltage capacitor tester is in the $800 plus range).

It is best if you can find a dealer or someone in your area with experience with tube gear to check your amp out.  At 10 years of age, your amp is pretty young.  My tube amp is about 15 years old, but, it is built mostly with parts that are in the 70-year age range (only the power transformer is "new").  I have not had to so much as replace a tube during this time.  

Why would the person need a multi meter when the amp comes with one built into the chassis and has markings for optimal bias?

For his future amp purchase?  Everybody needs a multimeter, unless you think a light bulb change needs a service call 😁.

I have had 3 (Tempest, Perseus, ST-100) Rogue products, all excellent, so you should be happy.

With these products, they are simple and cleanly laid out, I think you need to get comfortable with the insides. You will need to check the bias every 6 months, if you are going to change the output impedance, it is a simple wire change (if it is like what I've had), then there is any tube rolling which is on top with yours but requires general comfort with the product.

Good luck with it, I have nothing but positive stuff to say about Rogue and the people at Rogue are some of the best I have ever worked with.

For his future amp purchase? Everybody needs a multimeter, unless you think a light bulb change needs a service call 😁.

@russ69 Quite frankly if and when he upgrades from the already excellent Atlas Magnum, it should be a tube amp with auto-bias or at least similar built-in biasing tools (all Rogue amps have the same scheme). VAC even had a cool color LED-based biasing scheme before they went to full auto-bias. How many tube amps these days actually require a multimeter? It’s completely unnecessary and borderline sadistic. Weren’t you the "time marches on" guy in the coaxial thread? (lol - just ribbin' ya)

Yes, I have a multimeter. As far as my audio gear goes it’s only been needed for extremely dangerous and finicky electrostatic headphone amps. And once or twice to measure a speaker coil I thought was busted (it wasn’t, thankfully).

Agree with others regarding Rogue’s customer service being amazing!