The use of the chmod command might not be simple for beginners but there are several ftp clients that make this step very easy. Let's see how to do it on FileZilla:
Step 1 - Selecting the folderPress the right mouse button (right handed users) and select "File permissions".
Step 2 - Choosing the permissionCheck the permissions you want to apply to the folder or write the numeric value 755 in the shown text edit field.
Sometimes you could be asked to set more permissive writing attributes like 777, but you should be aware that you would be granting full control to "anybody" (not quite, but let's say it's true) and it could be dangerous!