a) A link requires some text you can click on. You write that text first, then you highlight it, then you click the Link button etc.
b) Auxclass is right. You've got too many images on your front page, and the files are too large. For visitors with a slow connection, the browser may even time out before loading all the images, and then those visitors will see nice big empty spaces instead of your images. You should
a) decrease the number of posts per page in settings > Reading;
b) use the read-more tag to truncate the posts;
c) upload and insert reasonably sized copies of your images. There's no point uploading and inserting 3888px wide images when the theme you're using displays them at 950px maximum: you increase the loading time of your pages and waste your storage space. Plus you get worse quality on the post, because images downsized by WP lose some color and sharpness - see here: