At level 46 you are able to access the Elemental Attributes page. I know your Astral App indicates that it is level 45, but lets face it there are so many bugs and other weird things going on in this game do not expect them to fix it anytime soon. This part of your heroes development will not include your Main Hero. The Main Heroes Elemental development will be int the skills section when you hit level 75. The Elemental Attributes are one of the most important stats to increase. The stats are important because it gives your heroes additional damage that is hard to resist early in the game, and it also gives your heroes additional resistances to Elemental damage. Elemental Attributes are also the most frustratingly difficult to increase even when done properly.
What method is considered to be done properly when developing Elemental Attributes?
By level 46 you should have at least one Striker or a Primary Tank that you will be dedicating more time in effort to leveling up and training than your other heroes. I will usually pick Night Sentinel as my Primary Striker early in the game, if starting late on a serve I would pick The Guardian because his skills can not be dodged.
Once you have chosen a Primary Striker or Tank and have the hero party ready it is now time to increase the heroes Elemental Attributes. At this point it must be remembered that every Elemental Crystal you earn will go into this hero until it is complete. If you decide to do other heroes at the same time the process of getting all the heroes done will take a lot longer than it should.
At the beginning raising the Attributes is fairly easy click on upgrade a few times and see which stat will come out a head of the three. In the case above Fire was appearing more frequently than Ice and Thunder. Once an Element has been decided focus only on that element. If it is decided to be Fire accept all plus 1 upgrades regardless of the out come of the other two Elements.
It is more ideal to take the plus 1 to fire than it is to let it pass by.