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

Under biased tubes in push pull designs will have a shorter useful life apart from audible distortion or any imbalances on imaging.

Under Biased (tube runs hot) you make your amp to distort and clip earlier at a volume control range.

Over biased (tube runs cold) you are somehow altering amp’s operation and crossover distortion can appear even at low volumes. May lead to slightly longer tube life but at the expense of sound quality.

So the perfect line for performance and tube life is somewhere in between.

Just to make things more complicated, some tubes like to be under biased, like 6550, kt66, kt88 and most likely kt120 and kt150, where you get good bass and good headroom. But rule of thumb is never exceed manufacturer’s nominal value more than 5-10%.

Besides that solid information from all above and especially this one from @mulveling and @yogiboy 

Let it warm up a few minutes. Watch for a too-hot bias (should not happen since we turned the bias way down as a precaution.

Make sure the speakers are connected . Just in case you didn't know that!

Enjoy your new tube amp.

I just want to say, get the meter you need to bias the amp. It's not very hard at all and I'm a total dummy on electrical stuff. I'm sure the manual tells you how to do it. It's not something to be feared it's just something new to learn. You got this. 

You've got a great amp. You can probably still get a manual online which gives all the instructions you need.

you will probably also need a cheap digital voltmeter - you can get them online - not sure of cost in Canada. Easy to bias the tubes, as the other posters have given great instructions. You can probably get the manual online and download and print it. And call them if you have questions.