Having trouble building on MY sims? :'(?

hi , i got the game yesterday . its the sims game where they are little mini sims and im having trouble building the garden pot for poppy . . i got so mad because i couldnt put the block where i wanted to because the thing where how its supposed to look (red and blue with a person standing as a visual) keeps getting in the way . . and i have it on wii . . how can i make it easier?