Just have to make sure the chain is as short as possible.
I've made a quick diagram to illustrate how the chain should be looking as you do it so if you feel like the chain is loose or something is wrong, you can look back and get a visual idea.
This could also be of help to anyone else who may struggle with chains in general out there.
1. So first you want to make the top tight which can be done by rolling the bike back. That will rotate the rear sprocket, and because the front can't turn (easily), that'll straighten it right up.
Hold the bottom chain together so that it is as straight as possible.
2. You want to make sure at the points you're holding, the chain will meet like that so that the master link can go on; two inside links meeting together.
If it isn't, just lengthen the chain a link extra from the side which has the outside link meeting so that you have two inner links together. Remove the rest of the chain from those two points you've found, and clip the master link on.
3. So now that the master link is on, you'll notice that the bottom part isn't straight; this would be because of the above situation more than likely, you had to add an extra link to the length to get the two inner links to meet.
4. Throw on the tensioner, put the wheel at the very top of the tensioner, push the tensioner as far back as possible. This will straighten up the bottom chain to look as illustrated.
You'll notice my bike doesn't have its chains perfectly tight; I'd admit it could be tighter but it works very well for me at the moment. Small fine tuning to be done here and there so the bikes work well, with a bit of tuning, work flawlessly.
Optional 5. Once you're set and everything is straight, lower the wheel on the tensioner a little to loosen the chain.
Found the post I read it from yesterday but forgot to copy it, but basically you don't want to the chain completely tight; it'll just damage things or wear them out quicker from all the tension. A bit of looseness still provides the tension required to run smoothly, and won't pull on the chain and gears too hard.
Someone correct me if I'm wrong about that; just what I read.
Well, if everything else is set and good to go; fuel up and enjoy the ride.
Tip. Mix the oil and fuel in a separate container together so you get a good thorough mix; pouring into the tank to shake the bike and mix works, but not ideal.
And, just go for it, no need for finesse. Throttle up and down, don't be afraid to go flat out here and there, but only for a short time each time.
You've probably read of that before, but thought I'd just make sure since we're all on the topic here and almost finally getting you on the road!