You can declare variables like this:
DECLARE @Var AS VARCHAR(MAX)
And you can assign them using a select statement like this:
SELECT @Var=MyColumn
FROM MyTable
WHERE <My Condition>
There are plenty of resources on TSQL if you google it.
In your situation, if you're sure you will have exactly three rows, you can use three separate select statements:
DECLARE @Var1 AS VARCHAR(MAX), @Var2 AS VARCHAR(MAX), @Var3 AS VARCHAR(MAX)
SELECT @Var1=MyColumn
FROM MyTable
WHERE <My Condition That Returns First Row>
SELECT @Var2=MyColumn
FROM MyTable
WHERE <My Condition That Returns Second Row>
SELECT @Var3=MyColumn
FROM MyTable
WHERE <My Condition That Returns Third Row>