Putting the 4 in the middle won't hurt really

use washers though.
Place the bracket on the wall in the required location and at correct height... use a decent spirit level to make sure its level then mark the holes.
Drill the holes using the correct sized SDS bit, make sure you drill straight and not deeper than the rawl bolt itself.
Usually you'll need to tap the bolts in with a hammer.. then place the bracket over the bolts that stick out the wall, put the nuts on and make sure its level.. once it's level and tight you can then put all the other bolts in.
Anchor bolts can be a pain in the arse at times so take your time and drill carefully else they tend to spin in the hole which isn't good.
When you screw those brackets to your TV you can adjust the height slightly but also you need to make sure the brackets are level on the back of TV else the TV will be wonky.. I have a very similar bracket
Good luck!