Some blocks have their own unique settings separate to the general settings options. To access these unique settings while creating an email or template, click the block directly instead of using the settings cog.
Image: You’ll see four settings tabs:
General: Click the Browse
icon to search through images in the Asset Library, and you can add the image by clicking the Use Asset 
icon.Size: In the Size tab you can edit the size of the image, either choosing to keep the original ratio the same or editing the height and width independently.
Border: you can choose to round the edges of the image, or just add a border as normal, you can choose the colour and the thickness too.
Mobile View: Resize on mobile to fit within the limits of the screen (this is non-ticked by default)
Button: You’ll see four settings tabs to change the button:
General: Add or remove the hyperlink, you can adjust the position, the height and width of the button.
Text: Edit the text, including font, weight, style, size, and colour.
Background: Change the colour, or select Options and change the button to an image.
Border: Add a border either inside or outside of the button, as well as rounding the edges.
Apply Style in all buttons: allows to replicate the style for all the buttons in the template.
Countdown: From the General tab you can edit the date for countdown. You can have this for a voucher expiry date for example. You can also change the colours, the size and the format of the countdown in the Background, Size, Format tabs.
For the blocks below, you'll have to hover on the panel, then click the three dots icon first:
Columns:
By default, the column block is two columns, you can increase this to up to eight columns.
You can drop any block into each column section.
In the settings for the column block, change the number of columns, change the size of each column and set them to stack on a mobile, and apply any border around the whole block.
Separator:
This is an an empty block to provide spacing within the email, you can turn this into a separating line.
By default the separator is blank and set to 20px high, you can change the background colour and height of the separator in the settings.
To turn the blank separator into a line separator, under Separator Line, change the type to Solid and change the width and heigh accordingly.
Container:
Using the container block, you can combine all other blocks and build some complex custom blocks. Nesting content together makes it easier when you're setting up dynamic rules.