How many columns?

Para mudar o número de colunas de posts que o seu tema tem, procure pelo código abaixo:
    #posts{
    float:center;
    {block:indexpage}
    width:O SEU NÚMERO AQUI;
    {/block:indexpage}
    {block:permalinkpage}
    width:600px;
    {/block:permalinkpage}
    z-index:999999;
    margin-left:120px;
    margin-top:15px;
    right:auto;
    background:transparent;
    margin-right:auto;
    position:relative;
    overflow-y:hidden;
    }

Onde diz "o seu número aqui" você coloca:
    1 coluna: 400px
    2 colunas: 600px
    3 colunas: 1000px
    4 colunas: 1200px
Consoante o número de colunas que quiser.

A seguir procure por photo, e encontrará um código assim:
    {block:IndexPage}<a href="{ReblogURL}" target="_blank"><img src="{PhotoURL-500}" alt="{PhotoAlt}" width=LARGURA DOS POSTS></a>{LinkCloseTag}</center>{/block:IndexPage}

Onde diz "largura dos posts" você coloca o mesmo número que usou para as colunas.
    Por exemplo, você quer 3 colunas, o código ficará desta forma:
        {block:IndexPage}<a href="{ReblogURL}" target="_blank"><img src="{PhotoURL-500}" alt="{PhotoAlt}" width=1000></a>{LinkCloseTag}</center>{/block:IndexPage}


x ----------------------------------------------------------------------------------------------------------------------------------- x


To change the number of posts columns that your theme has, look for the code below:
    #posts{
    float:center;
    {block:indexpage}
    width:YOUR NUMBER HERE;
    {/block:indexpage}
    {block:permalinkpage}
    width:600px;
    {/block:permalinkpage}
    z-index:999999;
    margin-left:120px;
    margin-top:15px;
    right:auto;
    background:transparent;
    margin-right:auto;
    position:relative;
    overflow-y:hidden;
    }

Where it says "your number here" you put:
    1 column: 400px
    2 columns: 600px
    3 columns: 1000px
    4 columns: 1200px
Depending on the number of columns you want.

Then search for photo, and you will find a code like this:
    {block:IndexPage}<a href="{ReblogURL}" target="_blank"><img src="{PhotoURL-500}" alt="{PhotoAlt}" width=POSTS WIDTH></a>{LinkCloseTag}</center>{/block:IndexPage}

Where it says "posts width" you enter the same number as you used for the columns.
    For example, you want 3 columns, the code will looks like this:
        {block:IndexPage}<a href="{ReblogURL}" target="_blank"><img src="{PhotoURL-500}" alt="{PhotoAlt}" width=1000></a>{LinkCloseTag}</center>{/block:IndexPage}