1. Login to your bank portal
2. Click send TAC
3. Fill in the TAC
4. Confirm
5. Double Confirm
6. Back to Lazada with the result of payment + order status(Price, discount etc)
7. Optional, you can fill in your 16 B Infinite number of your card to receive the point 60 day after order confirm

To earn more cash back, download a app named ShopBack, ask your friend around you that using ShopBack, get the invite link and invite reference code, both will get extra money in your ShopBack, then each time you want to purchase something, open Lazada from ShopBack, once is enough, it will record 99% of your order placed before you closed your Lazada App, so each time you want to purchase something, just open from ShopBack.
(Just saying, they still not providing a shortcut to place on your Phone Launcher to ease the action, kind of stupid for the developer. )

Emm, also remember to check the discount voucher provided by the seller, it is just on the bottom of your screen when you clicked into the item page.
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And also, I really recommend you to use your credit card, or your debit card, by using a card to make payment, you will only required to fill in your card number, your Name, expired date, and cvc2.
Then all your need is wait for sms, key in the TAC(some bank will auto send the TAC to you), click Enter on your soft keyboard or confirm button, then done.

No, don't save your card info into your account for safety, you will get fill in much, much more faster once your body memorize your card info, and you will speed up much faster than login to your online bank account.

The difference in between Online Bank payment and Credit/Debit card is, when there is refund happen, the money back to eWallet and required you to withdraw, for card, it back to your card.
And you got at least 0.1%, or 1% cash back for online shopping by using your credit card.
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And also, if you want to avoid all the trouble, avoid Lazada eWallet, as you can't withdraw your money from this eWallet, you can only top up and using it for purchase.
But, if you want maximize your discount/cash back if you purchase frequency, use it, but NOT now, you should wait for next promotion/activity, normally they will having a huge top up rebate for your first time top up, and cash back for every purchase you paid using Lazada eWallet.

So it depend, anyways, choose which one you like la.
For your shipping, no, except you are paying using the 7-11 payment method, the seller will be informed after you make payment with the payment confirm page show to you.
So unless the seller don't wanna honor your price, normally your item will be shipped by seller on 4-6 PM on the same day, and received by 2 day after.
For some items that sell on LazMall(like phone etc), you can choice express shipping, it cost some money, but if you place order on the morning, you will be receiving by evening today, or tomorrow at 12-2 PM noon.

And yes, your payment will be hold by Lazada, until the items is being confirm it is received by someone with the shipping company like LaZ Express, Gdex, NinjaVan, and Pos Laju, or seller own feet.(yes, it is allowed if same state)
Also remember, there is another platform named as Shopee, they also provide the voucher for the first time user, you can just register but not purchasing anything yet, and it will send new voucher to your account like every 2 weeks, with sometimes they provide extra voucher for limited type of electronic, so far I saw some TV, refrigerator etc.

Compare with Lazada eWallet, Shopee Coins is how you get rebate/extra discount for your purchase, seek for help on Shopee thread if you want to know more.