Start by memorizing the symbols and names. Sounds easy right? Well, not really. It looks easy but the thing that takes time and is tricky is to associate the count of objects with the symbols. To be used intuitively, "la" should not be associated with "one". Rather you should mentally picture descrete physical objects (or better, use real ones) to associate the symbols with the correct concept. This is the main reason separate symbols were chosen instead of just using "1","2","3".
Next it's time to memorize your addition table. Multi-digit addition can be done the same way you learned in grade school. Carry the extra digit for summing the next column...
Other exercises that can help are counting and mental addition. Try counting by "la's", "ti's" and "do's". Then start with "Ti" and count by "Do's".
Here's the table for multiplication. Multiplication by So and La are trivial so they are not shown.