most guest posting websites will allow you to insert 2 (sometimes even 3 links) into your guest post...
Use the 1st link to link out to one of the inner pages of your website using exact or partial match anchor (but if you're going to buy lots of guest posts each month, repeatedly, don't use ONLY exact / partial match anchors as this is very bad, for safety you will want 1-5% of the total anchors for that page to be exact match anchors, and 5-10% of the total anchors for that page to be partial match anchors, the rest of the anchors should be naked URLs, generic terms, etc..)
And the 2nd link on the page can point to your homepage with a branded anchor, or to one of the main categories of your site with exact / partial match anchor (exact / partial as in, it's the exact / partial name of the category)